Evaluation of alternative serum biomarkers to monitor the progression of chronic HBV and HCV infection.

Chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are among the most serious health conditions affecting about 600 million people worldwide leading to a number of severe liver diseases. Due to the lack of warning signs or mild symptoms during the early stage of the infection, a molecular signature associated with disease progression would be useful. Based on our recent paper where candidate biomarkers were determined through topological and modularity analysis of protein interaction networks (PINs), this study was focused on the evaluation of MIF, TNFRSF1A, FAS and TMSB4X as diagnostic biomarkers in chronic HBV and HCV infections. The aim was to establish a molecular profile, by combining those markers, that would discriminate the different stages during the progression of chronic hepatitis. One hundred and fifteen patients infected with HBV or HCV categorized into three groups: non-cirrhotic, cirrhotic and with HCC, and 20 healthy subjects were enrolled in this study. Serum levels of the aforementioned factors were measured by ELISA. TNFRSF1A serum levels appeared statistically significantly increased in all patient groups compared to control group with a p-value of <0.05. Furthermore, the combination of TNFRSF1A and TMSB4X serum levels successfully classified 63, 47% of patients indicating an association with HBV and HCV infections. Thus, variations of serum levels of TNFRSF1A and TMSB4X could be associated with the different stages of the disease and may be utilized for further research. On the other hand, we found no contribution of MIF and FAS serum levels for successful classification of patients.

Prostate cancer cell survival pathways activated by bone metastasis microenvironment.

The development of resistance to anti-cancer therapies in bones is a major hurdle preventing long-lasting clinical responses to anti-cancer therapies in hormone refractory prostate cancer. Herein, we present the major signal transduction pathways, which are activated in prostate cancer cells residing at bone metastasis microenvironment. These intracellular signal transduction pathways can inhibit anti-cancer therapy-induced apoptosis of metastatic prostate cancer cells, thereby optimizing their survival, locally. Employment of this knowledge in a clinical setting provides the conceptual framework for the development of bone-targeted therapies for advanced prostate cancer. Indeed, bone metastasis microenvironment-targeted therapies illustrate a novel paradigm in cancer treatment: anti-tumor treatment strategies may not only aim at directly inducing cancer cell apoptosis, but can also target the tumor metastasis microenvironment, and neutralize the protection it confers on metastatic cancer cells.

The Th1/Th2 cytokine balance changes with the progress of the immunopathological lesion of Sjogren's syndrome.

Expression of type-1 and type-2 cytokines at the mRNA level in labial salivary glands (LSG) of patients with Sjogren's syndrome (SS), as reported by several groups, have generated conflicting results. In the present study we have directly examined the production of IL-4, IL-13 and IFN-gamma by lymphocytes infiltrating the LSG of 44 consecutive patients referred for SS evaluation. Cytokines production was evaluated following in vitro culture of LSG in the presence of IL-2. IFN-gamma and IL-13 were detected in the majority of SN (24/44 and 26/44, respectively) while IL-4 was present in 5/44 SN. The presence of IFN-gamma was significantly higher in SS patients, as opposed to patients who did not fulfil the criteria for SS (P < 0.01). In addition, almost all cultured lymphocytes expressed mRNA for IFN-gamma (17/19 cultures) and IL-13 (18/19) while IL-4 mRNA was also expressed at high frequency (14/19 cultures). Interestingly, the IFN-gamma mRNA copies in cultured lymphocytes correlated significantly with the intensity of lymphocytic infiltration as evaluated by Chisholm's score (P < 0.01). Furthermore, RT-PCR of RNA extracted from whole LSG from 14 SS patients also demonstrated the presence of all cytokines in the majority of the cases and the prevalence of IFN-gamma in LSG with high-grade infiltration. Because IL-13 was produced by the majority of the cultured LSG, IgE production was also evaluated. Interestingly, IgE was detected in 21/44 LSG culture SN and mainly in those biopsies that had Chisholm's score less than 0.5 (P < 0.05). We conclude that lymphocytes infiltrating the LSG are capable of producing both Th1 and Th2 cytokines and that the balance between them shifts in favour of Th1 in LSG with high infiltration score and in patients with SS.

Adjuvant is the major parameter influencing the isotype profiles generated during immunization with a protein antigen, the Schistosoma mansoni Sm28-GST.

We have previously shown that immunization of mice with the vaccine candidate, the 28-kDa glutathione-S-transferase of Schistosoma mansoni (Sm28-GST), in alum or complete Freund's adjuvant, or with recombinant Salmonella typhimurium expressing Sm28-GST, induced type 2, mixed, or type 1 immune responses, respectively. In the present study we examined whether the genetic background, the dose and the route of antigen administration could modulate the profile of the immune response induced during these immunizations. Our results show that the nature of the adjuvant is the major factor that determines the profile of the response. Surprisingly, the genetic background did not influence the response, while the route of immunization, and to a lesser extent the dose of the antigen, weakly modulated the adjuvant-dependent orientation of the immune response.

The house dust mite allergen, Dermatophagoides pteronyssinus, promotes type 2 responses by modulating the balance between IL-4 and IFN-gamma.

A common property of allergens is their potential to generate type 2 cytokine responses. To understand the mechanisms involved in this phenomenon, we have evaluated the polarizing potential of a major allergen, Dermatophagoides pteronyssinus 1 (Der p 1), in an heterologous immunization system using the glutathione S-transferase of the parasite Schistosoma mansoni (Sm28-GST) as immunogen. In previous studies, we showed that immunization with the Sm28-GST emulsified in CFA induced a nonpolarized immune response. In contrast, when alum was used as adjuvant, a type 2 immune response was induced against Sm28-GST. Using this experimental model, we examined whether the administration of Der p 1 together with Sm28-GST influenced the nonpolarized and/or the Th2 profiles induced by the CFA or the alum immunization, respectively. Our results showed that the introduction of Der p 1 in the CFA immunization protocol was associated with diminished anti-Sm28-GST IgG2a Ab titers, reduced IFN-gamma mRNA expression, and frequency of IFN-gamma-producing cells. In contrast, the introduction of Der p 1 in the alum protocol did not affect IL-4 or Ig isotype responses. The effect of Der p 1 was specific, since coimmunization with tetanus toxin fragment C did not affect the profile of the response against Sm28-GST. Furthermore, inactivation of Der p 1 reduced its ability to modify the immune response profile, suggesting that its protease activity played an important role in deviating the immune response. Our results suggest that the Der p 1 has the ability to modify the profile of an immune response by modulating the balance between the polarizing cytokines IL-4 and IFN-gamma.

Infection with Salmonella typhimurium modulates the immune response to Schistosoma mansoni glutathione-S-transferase.

Immune response polarization is controlled by several factors, including cytokines, antigen-presenting cells, antigen dose, and others. We have previously shown that adjuvants and live vectors play a critical role in polarization. Thus, immunization with the Schistosoma mansoni 28-kDa glutathione-S-transferase (Sm28-GST) in aluminum hydroxide induced a type 2 cytokine profile and the production of immunoglobulin G1 (IgG1)- and IgE-specific antibodies. In contrast, mice infected with recombinant Salmonella typhimurium expressing Sm28-GST developed a type 1 cytokine profile and produced IgG2a-specific antibodies against Sm28-GST and Salmonella antigens. In this study, to determine if S. typhimurium not expressing Sm28-GST would still influence the type of the response against this antigen, we compared the profiles of the immune responses generated against Sm28-GST administered in alum in mice infected and not infected with S. typhimurium. Infected mice generated both IgG1 and IgG2a antibodies against Sm28-GST, while noninfected mice produced only IgG1 anti-Sm28-GST antibodies. Moreover, interleukin-4 (IL-4) mRNA expression in infected mice was near background levels, while gamma interferon (IFN-gamma) mRNA expression in coinfected mice was significantly higher than in mice immunized with Sm28-GST in alum only. However, after antigen-specific stimulation in vitro with Sm28-GST, levels of IL-4 and IFN-gamma cytokine production were similar in the two groups of mice. These results suggest that (i) the immune milieu produced during an infection may modify the response against an irrelevant antigen and (ii) isotype switching may be influenced by the cytokine environment of a bystander immune response, even though the specific antigen-driven cytokine production is not modified. Thus, the isotypic profile is not always an absolute reflection of the cytokines produced by antigen-specific Th cells.

In vivo induction of type 1 and 2 immune responses against protein antigens.

Polarization of the immune response towards Th1 or Th2 profiles is under the control of several, not yet well known, mechanisms. The present study was undertaken to investigate whether immune responses generated against major protein antigens, of parasitic (Schistosoma mansoni) and bacterial (Clostridium tetani) origin, present characteristic Th profiles. Mice were immunized with a single dose of S. mansoni 28 kDa glutathione-S-transferase (Sm28-GST) or tetanus toxin fragment c (TTc) in combination with different adjuvants, or Salmonelia typhimurium expressing these antigens as a fusion protein. Antigen-specific IgG isotypes and cytokine mRNA expression in vivo, as well as cytokine secretion after in vitro antigen stimulation were studied. Immunizations with either protein in aluminum hydroxide induced a strong Th2-associated antibody (IgG1) and cytokine (IL-4) response. In contrast, the recombinant S. typhimurium, expressing the TTc/Sm28-GST fusion protein, induced a Th1-like response, associated with the production of IFN-gamma and IgG2a antibodies against both antigens. When complete Freund's adjuvant was used, a non-polarized profile was observed, characterized by expression of both IL-4 and IFN-gamma, as well as strong specific IgG1 and IgG2a antibody responses. These results indicated that some protein antigens play a weak role in polarizing the immune response and that contrasting cytokine profiles could be induced against the same antigen, depending on the adjuvant employed.

An in vivo model of allergic inflammation: pulmonary human cell infiltrate in allergen-challenged allergic Hu-SCID mice.

CB.17 severe combined immunodeficient (SCID) mice were used to establish a model of allergic pulmonary inflammation. SCID mice were intraperitoneally reconstituted with 10(7) peripheral blood mononuclear cells (PBMC) from patients sensitive to Dermatophagoides pteronyssinus (Dpt) and 2 weeks later were exposed to Dpt aerosols. After Dpt nebulization, SCID mice engrafted with PBMC from Dpt-sensitive patients developed a specific human IgE response as well as an intense pulmonary infiltrate of human cells. In contrast, SCID mice reconstituted with PBMC from patients allergic to grass pollen or from non-allergic donors failed to produce IgE or to exhibit a similar inflammatory response. The level of the IgE production was dependent on the IgE level of the allergic donor. In the lungs of the same allergic SCID mice, 2 months after Dpt inhalation, the cell infiltrate contained CD45+, CD45RO+, CD20+ and HLA-DR+ human cells. They were located in perivascular and peribronchial areas and disseminated in the mouse lung parenchyma. Moreover, mRNA IL-5+ cells and eosinophils were found in peribronchial infiltrates. The observations indicate that humanized allergic SCID mice may develop, after nebulization with the relevant allergen, immune reactions similar to those observed in man and suggest that SCID mice may represent a useful model to analyze the regulatory mechanisms of IgE-associated allergic diseases.

Signal requirements for interleukin 4 promoter activation in human T cells.

We have studied the signal requirements for human IL-4 promoter activation in Jurkat T cells by the use of DNA transfection assays with vectors carrying the IL-4 promoter linked to a reporter gene. Stimulation with calcium (Ca2+) ionophores (ionomycin), but not with phorbol esters (phorbol myristate acetate, PMA) or cyclic AMP elevating agents (prostaglandin E2, PGE2), induced the transcriptional activity of the IL-4 promoter by approximately 3-fold. Costimulation with ionomycin and PGE2 resulted in the same level of IL-4 promoter activity as the stimulation with ionomycin alone. In contrast, costimulation with ionomycin and PMA decreased the activity of the IL-4 promoter by approximately 40% compared to stimulation with ionomycin alone. Induction of Il-4 promoter by ionomycin was partially inhibited (approximately 50% inhibition) in the presence of as high as 2 microgram/ml cyclosporin A (CsA), an inhibitor of the Ca+/calmodulin-dependent phosphatase calcineurin. Under the same conditions, only 0.1 microgram/ml of CsA inhibited by >95% the transactivation of the IL-2 promoter in response to ionomycin and PMA. Transfection of a deletion mutant of the calcineurin catalytic subunit (delta CaM-AI) known to have Ca2+-independent, constitutive phosphatase activity increased IL-4 promoter activity by approximately 14-fold. Stimulation with ionomycin of cells transfected with low doses of delta CaM-AI, further induced IL-4 promoter activity by approximately 2-fold. These results identify the Ca2+-signaling system as a key component of the signal transduction pathway leading to IL-4 promoter activation in Jurkat T cells and suggest a major role of calcineurin in its regulation.

CD28 activation promotes Th2 subset differentiation by human CD4+ cells.

Ligation of CD28 provides a costimulatory signal to T cells necessary for their activation resulting in increased interleukin (IL)-2 production in vitro, but its role in IL-4 and other cytokine production and functional differentiation of T helper (Th) cells remains uncertain. We studied the pattern of cytokine production by highly purified human adult and neonatal CD4+ T cells activated with anti-CD3, phorbol 12-myristate 13-acetate (PMA) and ionomycin, or phytohemagglutinin (PHA) in the presence or absence of anti-CD28 in repetitive stimulation-rest cycles. Initial stimulation of CD4+ cells with anti-CD3 (or the mitogens PHA or PMA+ionomycin) and anti-CD28 monoclonal antibodies induced IL-4, IL-5 and interferon-gamma (IFN-gamma) production and augmented IL-2 production (6- to 11-fold) compared to cells stimulated with anti-CD3 or mitogen alone. The anti-CD28-induced cytokine production corresponded with augmented IL-4 and IL-5 mRNA levels suggesting increased gene expression and/or mRNA stabilization. Most striking, however, was the progressively enhanced IL-4 and IL-5 production and diminished IL-2 and IFN-gamma production with repetitive consecutive cycles of CD28 stimulation. The enhanced Th2-like response correlated with an increased frequency of IL-4-secreting cells; up to 70% of the cells produced IL-4 on the third round of stimulation compared to only 5% after the first stimulation as determined by ELISPOT. CD28 activation also promoted a Th2 response in naive neonatal CD4+ cells, indicating that Th cells are induced to express a Th2 response rather than preferential expansion of already established Th2-type cells. This CD28-mediated response was IL-4 independent, since enhanced IL-5 production with repetitive stimulation cycles was not affected in the presence of neutralizing anti-IL-4 antibodies. These results indicate that CD28 activation may play an important role in the differentiation of the Th2 subset in humans.

Germline and productive C epsilon gene expression during in vivo IgE responses.

In vitro studies have established that Ig isotype switching typically involves deletion of CH genes that are located between VDJ and the CH gene that will be expressed, and is preceded by transcription of a germline (g) form of that CH gene. Increases in g epsilon transcript levels are induced by the cytokine IL-4, and always precede switching to IgE. To evaluate whether a similar relationship occurs in vivo, we examined IL-4 mRNA, g epsilon RNA, productive (p) epsilon mRNA, and serum IgE levels in two in vivo systems: one in which the injection of anti-IgD antibody induces mIgD+ B cells to switch to the expression of IgE and to secrete this isotype, and a second in which the injection of anti-IgE antibody stimulates IgE secretion by B cells that had been induced to express membrane IgE by earlier treatment with anti-IgD antibody. Increases in IL-4 transcript levels in anti-IgD-injected mice were followed within 24 h by increases in g epsilon RNA, and, one to two days later, by increased p epsilon mRNA and serum IgE levels. IL-4 antagonists blocked the g epsilon and p epsilon RNA and serum IgE responses in these mice, whereas the injection of otherwise untreated mice with IL-4 stimulated, within 24 h, a large increase in g epsilon RNA levels, followed 1-2 days later by a small increase in p epsilon mRNA. Injection of anti-IgD-primed mice with anti-IgE antibody also stimulated increases in IL-4, g epsilon and p epsilon RNA levels; however, the increases in IL-4 and g epsilon RNA were considerably smaller, and the increases in p epsilon mRNA and serum IgE considerably larger, than those observed in anti-IgD antibody-injected mice. IL-4 antagonists blocked the anti-IgE antibody-induced g epsilon RNA response, but not the p epsilon mRNA or serum IgE responses. Thus, IL-4 is required for the induction of g epsilon RNA in at least two in vivo systems, increased g epsilon RNA levels precede increases in p epsilon RNA levels in vivo as in vitro, and neither IL-4 nor g epsilon RNA is required to induce B cells that have already switched to IgE expression to differentiate into IgE-secreting cells.

Ig mu-epsilon isotype switch in IL-4-treated human B lymphoblastoid cells. Evidence for a sequential switch.

IgE is produced by B lymphocytes that have undergone a deletional rearrangement of their Ig H chain gene locus, a rearrangement that joins the switch region of the mu gene, S mu, with the corresponding region of the epsilon gene, S epsilon. To examine the resulting composite S mu-S epsilon junctions of human lymphoid cells, we have used a polymerase chain reaction strategy to clone the switch regions of the human myeloma U266 and of two IgE-producing human cell lines generated by treatment of lymphocytes with EBV plus IL-4. The switch junction of one of the EBV lines is a complex rearrangement in which a fragment of S gamma is interposed between S mu and S epsilon. This finding suggested that the switch to epsilon in this human lymphoid cell was preceded by a S mu-S gamma recombination. To determine whether this sequential switch rearrangement represented a unique event or occurred with some regularity in human B cells switching to IgE production, DNA samples from bulk cultures of lymphocytes treated with IL-4 were subjected to polymerase chain reaction amplification of their S mu-S epsilon junctions. When the resulting fragments were examined by Southern blotting, a substantial fraction hybridized to an S gamma probe. This finding suggests that sequential recombination involving S gamma is not rare in the switch to epsilon production in humans. Our polymerase chain reaction strategy should be useful in studying isotype switching at the DNA level.

Cholera toxin promotes the proliferation of anti-mu antibody-prestimulated human B cells.

The predominant effect of cholera toxin (CT) on cell growth has been postulated to be inhibitory as a result of its induction of intracellular cAMP. We have recently reported that CT selectively enhances surface DR expression while it inhibits anti-mu antibody-induced B lymphocyte proliferation. In the present series of experiments we studied the effect of CT on in vitro preactivated highly purified (greater than 95% CD20+) human B cells. Cholera toxin enhanced thymidine incorporation of anti-mu antibody-preactivated but not of Staphylococcus aureus Cowan I or PMA + ionomycin-preactivated B cells. Concentrations of 100 pg/ml CT stimulated an enhancement of thymidine incorporation equivalent to that of optimal doses of BCGF. The growth factor-like effect of CT required the complete molecule, since binding of purified B subunit (B-CT) to GM1 ganglioside by itself did not reproduce the holotoxin effect. Moreover, B-CT pretreatment of anti-mu antibody-primed cells completely neutralized the holotoxin-enhancing effect. Both PGE2, a physiological agent that stimulates intracellular cAMP elevation, and the cAMP analogue, 8-bromo-cAMP, mimicked the growth-promoting effect of CT. However, the ED50 of CT required to augment proliferation in anti-mu antibody-preactivated human B cells was approximately 100 times less than the ED50 for cAMP formation. These results demonstrate a specific growth factor-like promoting effect of CT on sIg-preactivated highly purified human B cells that may be mediated at least in part through elevation in intracellular cAMP levels. Increased DR expression and stimulation of growth of sIg preactivated B cells may explain some of the adjuvant properties of CT following orally or parenterally administered antigens.

Modulation of mouse complement receptors 1 and 2 suppresses antibody responses in vivo.

A mAb, 7G6, that binds to mouse CR1 and CR2 and down-modulates their expression on splenic B cells in vivo, was used to determine whether a decrease in CR1 and CR2 expression affects antibody responses to different T-dependent and T-independent Ag. Injection of mice with the mAb 7G6 prior to immunization with FITC haptenated Salmonella typhimurium (SH5771), Salmonella montevideo (SH5770), SRBC, or Ficoll dramatically decreased subsequent antibody responses to FITC. Although both IgM and IgG primary antibody responses were affected similarly, the antibody levels were most inhibited during early phases of the response. In contrast, down-modulation of the CR did not affect memory antibody responses, because injection of mice with 7G6 before a second immunization with FITC-SH5771 had no effect on subsequent anti-FITC antibody production. Moreover, polyclonal in vivo activation of the mouse immune system by anti-mouse IgD antibodies was not affected by previous administration of 7G6, because anti-IgD-induced increases in Ia expression and serum IgG1 levels were not affected. Taken together, these observations suggest that CR1 and CR2 may play an important role in enhancing primary antibody responses to many T-dependent and T-independent Ag and may contribute to a host's response to naturally occurring antigens such as bacteria.

Kinetics of interleukin-4 induction and interferon-gamma inhibition of IgE secretion by Epstein-Barr virus-infected human peripheral blood B cells.

Interleukin-4 (IL-4) acts directly on purified human peripheral blood B cells cultured in the presence of Epstein-Barr virus (EBV) to induce IgE secretion and to enhance the secretion of IgG and IgM. Interferon-gamma (IFN-gamma) inhibits IgE secretion in this system, without affecting the secretion of the other Ig isotypes. To identify the time period during which EBV-infected B cells can be induced by IL-4 to secrete IgE, we have studied the effects of delayed addition of IL-4, or the termination of IL-4 stimulation by wash out or by neutralization with anti-IL-4 antibodies, on the induction of an IgE response. To induce a maximal IgE response, IL-4 had to be added to cultures of B cells plus EBV no later than 2 days after the initiation of culture, and had to remain present through the tenth day of culture. These two time points correspond to the initiation of detectable DNA synthesis (Days 3 to 4) and the earliest detectable Ig secretion (Days 10 to 12) by EBV-stimulated B cells. No IgE response was induced if the period during which EBV-stimulated B cells were cultured with IL-4 was less than 4 days, or if IL-4 were added later than the tenth day of culture, regardless of how long the culture was continued beyond that time. In contrast, IL-4 considerably enhanced IgG and IgM secretion and B cell CD23 expression, even if it was added after the tenth day of culture. IFN-gamma strongly inhibited the IgE response of B cells cultured with IL-4 plus EBV if added within 6 days of the initiation of culture, but had little effect on the generation of IgM or IgG responses made by these cells, regardless of the time of addition. Neither IL-4 nor IFN-gamma affected ongoing IgE secretion by an established, IgE-secreting, EBV-transformed cell line. These observations suggest that: (i) IL-4 first becomes able to induce EBV-activated B cells to secrete IgE as these cells begin to synthesize DNA, must stimulate B cells for at least 4 days to induce IgE secretion, and loses its ability to induce IgE secretion as these cells differentiate into Ig-secreting cells; (ii) the ability of IFN-gamma to suppress an IgE response is limited to this same time period; and (iii) IL-4 enhancement of CD23 expression and IgM and IgG secretion are independent of IL-4 induction of an IgE response.

Generation and cloning of stable human IgE-secreting cells that have rearranged the C epsilon gene.

Although the secretion of Ig isotypes other than IgM is generally accompanied by a DNA rearrangement that deletes C mu (and the other IgCH genes located between VDJ and the expressed CH gene), a system has recently been described that generates a high frequency of IgE-secreting cells that have failed to delete IgCH genes or to rearrange their C epsilon genes. These cells, derived from EBV-transformed human PBMC, secrete IgM and IgD as well as IgE. To determine whether the absence of C epsilon rearrangement and CH gene deletion is a general phenomenon for human IgE-secreting cells, we have characterized IgE-secreting cells that are generated by culturing purified human B cells with EBV plus IL-4 in the presence of irradiated human PBMC. In contrast to the earlier observation, we have not been able to detect any cells that demonstrate cytoplasmic staining for IgE and concurrently stain for a second Ig isotype. Stable IgE-secreting cell lines and clones produced by this method have rearranged one of their C epsilon genes and have deleted both C mu genes. These observations demonstrate that the generation of human IgE-secreting cells can involve the same gene rearrangement and deletional mechanisms that lead to the generation of cells that secrete other isotypes.

Rapid stimulation of large specific antibody responses with conjugates of antigen and anti-IgD antibody.

Injection of mice with goat anti-mouse IgD antibody stimulates a large IgG1 anti-goat IgG antibody response, as well as polyclonal IgG1 production. To determine if this phenomenon could be used to induce large antibody responses to other Ag, covalent conjugates were produced between BSA or other Ag and H delta a/1, a mAb specific for IgD of the a allotype, and between BSA and AF3.33, a mAb specific for IgD of the b allotype. Injection of H delta a/1-BSA into BALB/c mice, which express Ig of the a allotype, or into (BALB/c x CB20)F1 mice (a x b allotype heterozygotes) induced IgG1 anti-BSA antibody responses that peaked 8 to 9 days after injection, and were more than 1000 times larger than those induced by injection of BSA alone, and 100 times larger than those induced by injecting unconjugated BSA plus H delta a/1. H delta a/1-BSA was no more immunogenic than unconjugated BSA when injected into CB20 mice, which express Ig of the b allotype, while AF3.33-BSA greatly enhanced anti-BSA antibody production in CB20, but not in BALB/c mice. Mice serially immunized with three different Ag conjugated to H delta a/1 made large antibody responses to all three Ag, provided that the mouse strain used did not recognize allotypic determinants on H delta a/1 as foreign and produce a neutralizing antibody response. Intravenous and s.c. routes of inoculation produced responses of similar magnitude and relatively low variability; responses to footpad or intramuscular inoculation were more variable, and i.p. inoculation induced smaller responses. Injection of BALB/c mice i.v. with 100 micrograms of H delta a/1-BSA induced an IgG1 anti-BSA response of 5.6 mg/ml, which was approximately 70% of the total IgG1 response. Anti-BSA responses to 30 micrograms of conjugate or less were much smaller, but could be considerably enhanced by adding unconjugated H delta a/1 to the inoculum. This system will be useful for the rapid stimulation of large antibody responses to biologically important Ag, and for investigating mechanisms of Ag processing and B and T cell activation.

Gene transcription during in vitro activation of human B lymphocytes with Staphylococcus aureus Cowan I strain.

With the use of nuclear transcription run-off assays we have determined the kinetics of transcriptional activity for the c-fos, c-myc, DR beta, DQ beta, (TfR), Blast-1, and Ig kappa genes in human tonsillar B lymphocytes of high to intermediate density after stimulation with Staphylococcus aureus Cowan I strain (SAC). Nuclei were isolated at various times after stimulation with SAC. Stimulation with SAC resulted in significant increase in the transcription of all of the genes. Maximum expression of the c-fos, transferrin receptor, DR beta, and DQ beta genes was obtained within 0.5 h after stimulation. Maximum expression of c-myc and Blast-1 was obtained within 3 h. Peak expression of Ig kappa was observed at 8 h. Transcriptional activities of all genes examined, except for the Blast-1 and Ig kappa, decreased rapidly after their respective peaks; they remained at higher levels than their base line. Inhibition of protein synthesis by cycloheximide did not significantly affect the kinetics of transcription of these genes. These data demonstrate the cascade of transcriptional activity of various genes associated with human B cell activation and indicate that the induction of their transcription is independent of de novo protein synthesis.

Enumeration of IgE secreting B cells. A filter spot-ELISA.

To assess the frequency of IgE producing cells in humans a filter immunoplaque assay has been developed to detect IgE secretion from individual B lymphocytes in unfractionated peripheral blood mononuclear cells (PBMC). PBMC were incubated in microfilter plates containing nitrocellulose membranes coated with polyclonal anti-human IgE antibody, and the IgE production by a single cell was detected using a specific anti-human IgE monoclonal antibody followed by enzymatic development. The products of the enzymatic reaction were visualized as blue plaques on the membranes. The assay was both sensitive and specific as determined by: (1) a near 1:1 correlation between direct cell counts of an IgE producing myeloma cell line (U266) and the number of plaques in the filter immunoassay; and (2) the absence of detectable plaques generated by human B cells transformed by Epstein-Barr Virus (EBV) and producing only IgG or IgM. The presence of other cell types in PBMC did not affect the ability to detect IgE secreting cells. Replicate cultures of highly purified B lymphocytes, first transformed with EBV and then stimulated with recombinant human interleukin-4, produced IgE levels in culture supernatants that correlated closely with the number of IgE producing cells (r = 0.93; P less than 0.001). Furthermore, using the same transformed cells, the number of IgE secreting cells assessed by the immunoplaque assay was significantly correlated (r = 0.94; P = 0.002) with the number of IgE producing cells assessed by immunofluorescence staining of intracytoplasmic IgE. This assay provides a simple and direct method to assess the frequency of IgE producing lymphocytes in humans.