Antigen conjugated to anti-CD23 antibodies is rapidly transported to splenic follicles by recirculating B cells.

IgE-antigen complexes, administered intravenously to mice, induce a several 100-fold higher specific antibody response than antigen alone. Additionally, in vivo activation and proliferation of specific CD4(+) T cells is enhanced. The mechanism behind these effects is thought to be that peripheral B cells capture IgE-antigen complexes via their low-affinity receptor for IgE, CD23, and rapidly transport them to splenic B cell follicles where an immune response is initiated. Here, we demonstrate that ovalbumin, covalently coupled to anti-CD23 antibodies and administered intravenously to mice, is also transported to splenic follicles and induces an enhanced primary antibody response. These effects are absent in CD23-deficient mice. No enhanced induction of immunological memory was observed. These findings extend previous observations regarding the in vivo role of CD23 and emphasize that recirculating B cells play an important role in antigen transport to the spleen.

[Genital lymphedema associated with Crohn's disease]. / Lymphœdème génital associé à une maladie de Crohn.

INTRODUCTION: Crohn's disease is a chronic inflammatory intestinal pathology which can be associated to different extra-digestive manifestations. We reported a case of recurrent genital lymphedema leading to Crohn's disease diagnosis. CASE REPORT: A 49-year-old man was referred for increased penis and scrotal volume, associated with recurrent febrile flare during the 10 previous years. Clinically, we noted an inflammatory penis and scrotum lymphedema. Clinical urological examination, and biological, bacteriological, computer-tomography examinations were negative. Metastatic Crohn's disease was diagnosed in association with concomitant severe terminal ileitis. Treatment with corticosteroids and azathioprine resulted in significant decrease of inflammatory genital lymphedema. CONCLUSION: Genital inflammatory lymphedema occurs during inflammatory, infectious, and tumor diseases. Some cases of metastatic genital lymphedema related to Crohn's disease are described, most often in children. Inflammatory genital lymphedema associated with gastrointestinal symptoms may suggest Crohn's disease.

Committed mast cell progenitors in mouse blood differ in maturity between Th1 and Th2 strains.

Mast cell progenitors (MCp) leave the bone marrow and migrate to peripheral tissues where they mature. Although the existence of committed MCp in adult mouse and human blood has been postulated, they have never been found. We have isolated a rare population of cells in adult mouse blood, committed to the mast cell lineage. These were identified as lineage- c-kit(hi) ST2+ integrin ß7(hi) CD16/32(hi) cells. Moreover, a major difference in maturity of these cells based on FcεRI expression was observed between the Th2-prone BALB/c strain and the Th1-prone C57BL/6 strain (66% vs. 25% FcεRI+, respectively). Therefore, the choice of mouse strain is critical when studying disease models such as experimental asthma where mast cells and their progenitors are involved.

Complications of intestinal stomas.

BACKGROUND: Stomal complications are prevalent and associated with considerable morbidity. This study examined the incidence and potential risk factors for their development. METHODS: The time of onset and presence of ten specific complications were recorded for patients with an intestinal stoma over 10 years at two urban hospitals. A database was established with 20 explanatory variables (such as common medical co-morbidities) derived from the stomatherapy and medical records. Univariable and multivariable analyses were performed to identify potential risk factors for the development of complications. RESULTS: Some 1216 patients (mean age 64 years) with a minimum of 2 years' follow-up were included, of whom 544 (44·7 per cent) underwent surgery for malignancy and 647 (53·2 per cent) had a colostomy formed. There were 1219 complications in total; 807 major complications (excluding excoriation and slough) occurred in 564 patients (46·4 per cent), of which the commonest was parastomal hernia (171, 14·1 per cent). On multivariable analysis, musculoskeletal co-morbidity (odds ratio (OR) 1·79, 95 per cent confidence interval 1·05 to 3·07; P = 0·032), cancer (OR 1·48, 1·13 to 1·93; P = 0·004) and high American Association of Anesthesiologists score (OR = 3·80, 2·14 to 6·75; P < 0·001) were associated with an increased risk of complications. Preoperative siting was associated with a reduced risk (OR 0·59, 0·39 to 0·90; P = 0·014). CONCLUSION: Intestinal stomal complications are common, occurring in almost half of patients. There are certain irremediable risk factors, allowing appropriate preoperative counselling.

Studies on the mechanism by which antigen-specific IgG suppresses primary antibody responses: evidence for epitope masking and decreased localization of antigen in the spleen.

Immunoglobulin (IgG) has the ability to suppress the Ab response against the Ag to which it binds. Although the mechanism remains unclear, this phenomenon has physiological relevance and is used clinically in Rh prophylaxis. As suppression works well in mice lacking the inhibitory FcgammaRIIB, the two most likely explanations are that IgG masks epitopes and/or that IgG increases the clearance of Ag. In the present study, mice were immunized with sheep red blood cells (SRBC) to which the hapten 5-iodo-4-hydroxyl-3-nitrophenacetyl (NIP) was conjugated at high or low density and the ability of IgG anti-NIP to suppress the Ab response to NIP and SRBC was assayed. Only the NIP-specific response was suppressed when mice were immunized with SRBC-NIP(low), whereas both NIP- and SRBC-specific responses were suppressed when SRBC-NIP(high) was used. This is best explained by epitope masking; at high epitope density, IgG also blocks neighbouring epitopes from recognition by B cells. We also examined the effects of IgG-mediated suppression on T-cell responses directly in vivo. While IgG anti-SRBC administered with sheep red blood cells ovalbumin (SRBC-OVA) almost completely suppressed the anti-SRBC and anti-OVA Ab responses, the OVA-specific T-cell response was still 50% of that observed in control mice. This is probably the result of decreased Ag exposure as IgG-bound SRBC were cleared faster from the bloodstream and were found at lower concentration in the spleen than unbound SRBC. These results suggest that both Ag clearance and epitope masking occurs during IgG-mediated suppression, but that under physiological circumstances epitope masking is the predominant mechanism.

Impaired antibody responses but normal proliferation of specific CD4+ T cells in mice lacking complement receptors 1 and 2.

Severely impaired Ab responses are seen in animals lacking C (complement) factors C2, C3 or C4 as well as CR1/2 (C receptors 1 and 2). The molecular mechanism behind this phenomenon is not understood. One possibility is that C-containing immune complexes are endocytosed via CR2 on B cells and presented to specific CD4+ T cells, which would then proliferate and provide efficient help to specific B cells. In vitro, B cells can endocytose immune complexes via CR1/2 and present the Ag to T cells. Whether absence of this Ag presenting function in Cr2(-/-) mice (mice lacking CR1/2) explains their low Ab response is unclear. To address this question, Cr2(-/-) and wild type mice were transferred with OVA-specific T cells, obtained from the DO11.10 strain which has a transgenic TCR recognizing an OVA peptide. The animals were subsequently immunized with sheep red blood cells (SRBC) conjugated to OVA. Interestingly, proliferation of the OVA-specific T cells was normal in Cr2(-/-) mice, although their Ab response to both SRBC and OVA was severely impaired. These observations suggest that the impaired Ab response in Cr2(-/-) mice cannot be explained by a lack of appropriate induction of T cell help.

IgE enhances specific antibody and T-cell responses in mice overexpressing CD23.

IgE administered with its specific antigen in vivo induces enhanced proliferation of specific T cells as well as enhanced production of specific antibodies. Both effects are dependent on the low-affinity receptor for IgE (CD23) and the underlying mechanism is thought to be increased antigen presentation following uptake of IgE/antigen complexes via CD23(+) B cells. By contrast, CD23 negatively regulates antibody responses to antigens administered with alum, i.e. without IgE. This effect has been observed as low IgG1 and IgE responses in transgenic mice overexpressing CD23 (CD23Tg). The present study was designed to test whether IgE could enhance antibody and T-cell responses in CD23Tg animals or whether CD23's downregulatory effect precludes IgE-mediated enhancement. IgE-anti-TNP administered with OVA-TNP enhances the OVA-specific antibody responses in wild-type (wt) and CD23Tg mice equally well. Interestingly, the total magnitude of antibody responses to IgE + OVA-TNP and to uncomplexed OVA-TNP, as well as to sheep erythrocytes and keyhole limpet haemocyanine, were lower in the CD23Tg mice. IgE induced proliferation of OVA-specific CD4(+) T cells to the same degree in wt and CD23Tg mice. The effect on T cells was dependent on CD23(+) B cells as demonstrated in in vitro proliferation assays. In conclusion, CD23 does indeed have dual immunoregulatory effects in the same animal. The receptor mediates enhancement of antibody and T-cell responses to IgE-complexed antigen, most likely via increased presentation of complexed antigen, while it negatively regulates the total antibody response to a variety of antigens.

Antibody-mediated regulation of the immune response.

Antibodies administered in vivo together with the antigen they are specific for can regulate the immune response to that antigen. This phenomenon is called antibody-mediated feedback regulation and has been known for over 100 years. Both passively administered and actively produced antibodies exert immunoregulatory functions. Feedback regulation can be either positive or negative, resulting in >1000-fold enhancement or >99% suppression of the specific antibody response. Usually, the response to the entire antigen is up- or downregulated, regardless of which epitope the regulating antibody recognizes. IgG of all isotypes can suppress responses to large particulate antigens like erythrocytes, a phenomenon used clinically in Rhesus prophylaxis. IgG suppression works in mice lacking the known Fc-gamma receptors (FcgammaR) and a likely mechanism of action is epitope masking. IgG1, IgG2a and IgG2b administered together with soluble protein antigens will enhance antibody and CD4+ T-cell responses via activating FcgammaR, probably via increased antigen presentation by dendritic cells. IgG3 as well as IgM also enhance antibody responses but their effects are dependent on their ability to activate complement. A possible mechanism is increased B-cell activation caused by immune complexes co-crosslinking the B-cell receptor with the complement-receptor 2/CD19 receptor complex, known to lower the threshold for B-cell activation. IgE-antibodies enhance antibody and CD4+ T-cell responses to small soluble proteins. This effect is entirely dependent on the low-affinity receptor for IgE, CD23, the mechanism probably being increased antigen presentation by CD23+ B cells.

IgG3-mediated enhancement of the antibody response is normal in Fc gammaRI-deficient mice.

Antibodies, administered together with their specific antigen, can feedback-regulate antibody responses to this antigen. IgG1, IgG2a and IgG2b enhance antibody responses to soluble protein antigens. This effect is primarily mediated by FcRs as enhancement is impaired in FcR gamma-/- mice, reported to lack Fc gammaRI and Fc gammaRIII because of deletion of the common FcR gamma chain. Also IgG3 can enhance antibody responses. However, this effect is unperturbed in FcR gamma-/- mice but severely impaired in complement-depleted animals and in animals lacking complement receptor 1 and 2. Although this argues against involvement of Fc gammaRs, FcR gamma-/- mice may express one-fifth of the normal levels of Fc gammaRI and, in addition, Fc gammaRI has been suggested to bind IgG3. We re-investigated the dependence of IgG3-mediated enhancement on Fc gammaRs using a mouse strain selectively lacking Fc gammaRI and found that IgG3-mediated enhancement is completely normal. Unlike IgE and IgG2a, which are both thought to enhance T-cell proliferation via FcR-mediated antigen presentation, IgG3 was a poor enhancer of T-cell proliferation both in vivo and in vitro. These findings argue against a significant involvement of Fc gammaRs in IgG3-mediated enhancement of antibody responses and support our previous conclusion that complement plays a major role.

Patients' views on follow up of colorectal cancer: implications for risk communication and decision making.

BACKGROUND: Medical views about the clinical value and potential detrimental effect on quality of life of postoperative follow up are divided. There is no literature on the views of British patients with colorectal cancer towards the follow up process. AIM: To investigate patients' views and experiences of follow up of colorectal cancer, and to assess their attitudes towards suggested changes to follow up policy. PATIENTS AND METHODS: A total of 156 asymptomatic and disease-free patients with colorectal cancer were identified from the follow up clinic. Recurrence-free status was confirmed through retrieval of computerised clinic letters. A postal survey using a 39 item piloted questionnaire was undertaken. Data analysis generated descriptive statistics and logistic regression models. RESULTS: A response rate of 61% (95) was obtained. Among these respondents, 63% (60) had undergone initial surgery within three years of the time of the survey, and 86% (82) patients expected a further follow up appointment. Majorities of the sample, ranging from 71% (67) to 96% (91), expressed satisfaction with respect to clinic delays, staff conduct and knowledge about their case, consultation time, and being able to discuss personal problems freely. However some patients reported difficulty in discussing sexual problems at the clinic. Appointment imminence caused anxiety, sleep problems, and decreased appetite in 35% (35), 27% (26), and 8 % (8) of patients respectively. However, 78% (74) patients felt reassured and optimistic for the future after receiving results. Such optimism is not necessarily justified in terms of estimated mortality risks. A majority (78%, 66) stated that they would value finding out about the presence of recurrence even if there would be no survival benefit. Nearly half of the sample (48%, 43) felt that they would disagree with the cessation of follow up in any circumstances. Only 47% (42) and 27% (24) indicated that they would accept follow up by a specialist nurse or their general practitioner, respectively. Attitude to follow up was unrelated to reported anxiety before appointments. Only 22% (19) of the sample could identify risk indicators for recurrence, but 64% (61) agreed that they would like to be told what to look for. DISCUSSION: A sample of patients with colorectal cancer expressed a high degree of satisfaction with hospital follow up. Although a substantial minority reported suffering from pre-visit anxiety, most felt that this disadvantage was compensated for by reassuring results, and believed that investigations did not have a significant negative impact on their quality of life. Respondents valued hospital follow up, and half would reject complete discharge or alternative forms of follow up. These findings demonstrate that patients have a different perception of the risk of recurrence than clinicians who would consider the survival prospects for most patients to be more or less unaffected by follow up interventions. Attempted modifications to follow up policies should be introduced with caution, and should take account of patient understanding of medical reasoning. The findings also raise questions about risk communication with patients.

FcgammaRIIB in IgG-mediated suppression of antibody responses: different impact in vivo and in vitro.

The suppressive effect of IgG on Ab responses to particulate Ags such as erythrocytes is well documented. IgG-mediated suppression is used clinically in rhesus prophylaxis to prevent RhD-negative mothers from becoming immunized against their Rh D-positive fetuses. We have recently shown that IgG anti-SRBC, passively administered together with SRBC, can induce efficient suppression of primary Ab responses to SRBC in mice lacking the known FcRs for IgG (FcgammaRI, FcgammaIII, and FcgammaRIIB or the neonatal FcR). The lack of a demonstrable effect of the inhibitory FcgammaRIIB was particularly surprising, and, in this study, the involvement of this receptor is further investigated during broader experimental conditions. The data show that SRBC-specific IgG administered up to 5 days after SRBC can induce suppression both in wild-type and FcgammaRIIB-deficient mice. Suppression of secondary Ab responses to SRBC in vivo was similar in the two strains. In contrast, IgG-mediated suppression of Ab responses in vitro was impaired in cultures with primed FcgammaRIIB-deficient spleen cells. In conclusion, inhibition of in vivo Ab responses to SRBC by passively administered IgG can take place via an FcgammaRIIB-independent pathway. This pathway causes >99% suppression and operates during all experimental conditions studied so far. The nature of the mechanism can at present only be hypothesized. Masking of epitopes and/or rapid elimination of IgG-Ag complexes would both be compatible with the observations.

IgG2a-mediated enhancement of antibody responses is dependent on FcRgamma+ bone marrow-derived cells.

Antibodies (Ab) administered in complex with antigens (Ag) have the capacity to regulate the out-coming specific immune response. Primary immunization with complexes of bovine serum albumin-2,4,6-trinitrophenyl (BSA-TNP) and immunoglobulin (Ig)G2a anti-TNP induced a significant enhancement of IgG1 and IgG2a BSA-specific Ab response compared to immunization with the Ag alone. Enhancement was absent in nude mice, demonstrating the requirement of T cells for this regulation. Secondary immunization with BSA alone in mice previously primed with BSA-TNP/IgG2a led to a dramatic increase of Ab production, showing that immune complexes are efficient inducers of immunological memory. IgG-mediated enhancement of Ab responses has previously been shown to be impaired in mice lacking FcgammaRI, FcgammaRIII and FcepsilonRI owing to gene targeting of the common FcRgamma subunit (FcRgamma-/-). Here we show that enhancement after immunization with BSA-TNP/IgG2a complexes is restored in irradiated FcRgamma-/- recipients transferred with wild-type (FcRgamma+/+) bone marrow (BM) cells. In contrast, no enhancement is seen in FcRgamma+/+ irradiated animals reconstituted with FcRgamma-/- BM cells. We conclude that IgG2a-mediated enhancement of Ab responses is dependent on the presence of FcgammaRI and/or FcgammaRIII on BM-derived cells and that the presence of these receptors on the radioresistant follicular dendritic cell is not essential.

IgE-mediated suppression of primary antibody responses in vivo.

The ability of immunoglobulin (Ig)G to feedback suppress antibody (Ab) responses is a well known property clinically used to prevent haemolytic disease of newborns. We recently found that IgG was able to suppress the primary Ab response to sheep red blood cells (SRBC) in mice lacking the known Fc-receptors for IgG. In addition, IgE and F(ab')2 fragments of IgG were able to suppress the response to SRBC in wild-type mice. These results suggested that the IgG-mediated suppression can take place independently of the IgG (Fc) portion and that masking of the epitopes is an important mechanism. In the present report we investigated whether the suppression caused by IgE is Fc-dependent. Monoclonal IgE anti-2,4,6-trinitrophenyl (TNP), administered with TNP-coupled SRBC (SRBC-TNP), can induce an efficient suppression in mice lacking FcgammaRI + RIII + FcepsilonRI (owing to the lack of the common gamma chain, FcRgamma), FcgammaRIIB or FcepsilonRII (CD23). Because the known IgE-binding receptors are FcepsilonRI, CD23, FcgammaRIIB and FcgammaRIII, the results suggest that also the IgE-mediated suppression can take place independently of the Fc-receptors. A slightly less efficient suppression in CD23-deficient animals, suggests a minor involvement of this receptor.

Immune complex-mediated enhancement of antibody responses without induction of delayed-type hypersensitivity.

Immunoglobulin (Ig)G and IgE antibodies enhance the humoral response in vivo to soluble antigens with which they form complexes. In vitro, antigen is targeted to B cells by IgE antibodies and to macrophages and dendritic cells (DCs) by IgG, thus leading to increased antigen presentation to specific T cells. Possibly these mechanisms are also responsible for antibody-mediated enhancement in vivo. We now address the question of whether IgG- and/or IgE-antigen complexes can prime for delayed-type hypersensitivity (DTH), a reaction known to require primed T helper (Th)1 cells. Mice were immunized with IgG-anti-2,4,6-trinitrophenyl (TNP)/BSA-TNP or IgE-anti-TNP/BSA-TNP. Mice given BSA-TNP alone or BSA-TNP in complete Freund's adjuvans (CFA) were used as controls. DTH and IgG-anti-BSA levels were measured after subsequent challenge with BSA. A potent BSA-specific antibody response was induced by IgE- or IgG-complexed antigen as well as by CFA/antigen but DTH-reactions were only observed in mice immunized with CFA/antigen. Both IgE and IgG enhanced the production of BSA-specific IgG1, IgG2a and IgG2b, although the most pronounced enhancement was seen in the production of IgG1. These findings suggest that Th2 cells rather than Th1 cells are involved in the immune response to IgG- and IgE-immune complexes.