Glatiramer acetate treatment directly targets CD11b(+)Ly6G(-) monocytes and enhances the suppression of autoreactive T cells in experimental autoimmune encephalomyelitis.

Glatiramer acetate (GA) is used for the treatment of relapsing-remitting multiple sclerosis (MS) and can suppress experimental autoimmune encephalomyelitis in animals. Effective GA treatment is associated with the induction of anti-inflammatory T(H)2 responses and antigen-specific expansion of CD25(+)/Foxp3(+) Tregs through the modulation of antigen-presenting cells. Here, we show that intravenous injection of fluorochrome-labelled GA resulted in rapid and specific binding of GA to CD11b(+) F4/80(lo) Ly6G(-) blood monocytes via an MHC class II-independent mechanism. Intravenous GA treatment enhanced the intrinsic capability of these monocytes to directly suppress T cell proliferation in vitro. The suppressive function correlated with reduced proliferation of myelin-specific T cells in vivo after intravenous GA treatment. In contrast, subcutaneous treatment with GA inhibited the pro-inflammatory IFNγ-producing T cell phenotype rather than suppressing T cell proliferation. These data indicate that (1) GA engages directly with circulating monocytes to induce type II monocyte suppressor function; and (2) the therapeutic efficacy of GA may be expanded by employing different routes of GA administration to engage alternative mechanisms of suppression of autoreactive T cells in MS.

Partial depletion of CD69low-expressing natural regulatory T cells with the anti-CD25 monoclonal antibody PC61.

The role CD4(+) CD25(+) regulatory T cells (Treg) play in modulating the immune response has been investigated extensively over recent years. Much of the work to date has used the activation marker CD25 to define, enrich and deplete Treg. However, the identification of FoxP3 as a definitive marker of Treg has allowed us to study the effect of monoclonal antibodies against CD25 on regulatory T-cell populations. Recently, published data have indicated that Treg are inactivated, not depleted, through treatment with anti-CD25 monoclonal antibody. Using FoxP3-Green fluorescent protein reporter mice, we show that treatment with the CD25 MoAb PC61 depleted a subpopulation of Treg. The depleted Treg population expressed low levels of the CD69 marker, indicating an inactive phenotype. In addition, PC61 treatment altered the function of the remaining regulatory T-cell population, preventing their ability to modulate autoimmune diseases. Thus, our results have important implications with regard to interpreting experimental outcomes from in vivo anti-CD25 treatments.

Peloruside A enhances apoptosis in H-ras-transformed cells and is cytotoxic to proliferating T cells.

Peloruside A (peloruside), a compound isolated from the marine sponge Mycale hentscheli , inhibits growth of human (HL-60) and mouse (32D-ras) myeloid leukemic cells, as well as non-transformed 32D cells. Using the MTT cell proliferation assay and trypan blue dye exclusion tests, little difference was seen in growth inhibition between 32D and 32D- ras cells; however, peloruside was more cytotoxic to the oncogene-transformed cells. Peloruside also blocked 32D- ras cells more readily in G2/M of the cell cycle, leading to apoptosis. Annexin-V/propidium iodide staining of 32D and 32D- ras cells showed that 1.6 microM peloruside induced significant cell death by 36 hours in 32D cells (16% survival), but to comparable levels as early as 14 hours in 32D- ras cells (11% survival). There was no evidence for activation of either of the initiator caspases-8 or -9 by 0.1 microM peloruside following 12 hours of exposure. Peloruside inhibited T cell proliferation and IL-2 and IFN gamma production in both the mixed lymphocyte reaction and following CD3 cross-linking, and this effect was shown to be a non-specific cytotoxic effect. It is concluded that peloruside preferentially targets oncogene-transformed cells over non-transformed cells by inducing transformed cells to undergo apoptosis.

A simplified cytokine immunoassay using magnetic polymer particles.

Accurate detection of cytokines is essential for understanding their biological role in the immune system. Various methods to detect cytokines have been developed, including sandwich enzyme-linked immunosorbent assay (ELISA) and flow cytometry-based methods. All of the currently available methods have limitations, however. These limitations include time and extensive handling in standard sandwich ELISAs and the need for specialized equipment in flow cytometry-based assays. We have developed a magnetic polymer cytokine immunoassay and demonstrate that this assay is rapid and simple, needs less handling and offers better dynamic range, compared to standard sandwich ELISA. Furthermore, it does not require flow cytometry equipment, which is often used in microparticle-based polymer immunoassays. The magnetic polymer cytokine immunoassay described in this study is as sensitive as a standard sandwich ELISA. Because the method is not limited to the use of magnetic polymer particles, it is versatile and compatible with a number of different solid matrixes.

Importance of the T cell receptor alpha-chain transmembrane distal region for assembly with cognate subunits.

Antigen recognition by alphabeta T lymphocytes is mediated via the multisubunit TCR complex consisting of invariant CD3gamma,delta,epsilon and zeta chains associated with clonotypic TCRalpha and beta molecules. Charged amino acids located centrally within the TCRalpha transmembrane region are necessary and sufficient for assembly with the CD3deltaepsilon heterodimer. Previously, we have shown that deletion of 6-12 amino acids from the carboxy terminus of the TCRalpha-chain dramatically abrogates surface TCR expression, suggesting that the distal portion of the TCRalpha transmembrane region contains information that regulates the assembly and/or intracellular transport of TCR complexes. We have examined in more detail the molecular basis for reduced TCR expression in T cells bearing truncated TCRalpha chains. We found that in contrast to wild-type (wt), variant TCRalpha proteins missing the last nine C-terminal amino acids did not associate with core CD3gamma,delta,epsilon chains and were not assembled into disulphide-linked alphabeta heterodimers. The stability of newly synthesised wt and variant TCRalpha molecules was similar, showing that the abrogated surface TCR expression was not a consequence of impaired protein survival. Nevertheless, truncated TCRalpha chains still assembled with the chaperon protein calnexin in the endoplasmic reticulum, indicating that the distal portion of the TCRalpha transmembrane region is not essential for calnexin interaction. These data document a role for the distal portion of the TCRalpha transmembrane region in the assembly of TCR complexes and provide a molecular basis for reduced TCR expression in cells bearing truncated TCRalpha chains.

The novel cytotoxic sponge metabolite peloruside A, structurally similar to bryostatin-1, has unique bioactivity independent of protein kinase C.

A novel secondary sponge metabolite, peloruside A (peloruside), isolated from the marine sponge Mycale sp. (New Zealand), was tested for its cytotoxic effects on mammalian cells in culture. The macrolide structure of peloruside is similar to that of the protein kinase C (PKC) activator, bryostatin-1 (bryostatin), both containing a pyranose ring adjacent to a gemdimethyl moiety. Peloruside is a potent inhibitor of cell proliferation. Treatment of different mammalian cell lines with peloruside for 48-96 h gave IC50 values ranging from 4 to 15 nM, using the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium (MTT) cell proliferation assay. Peloruside was shown to be both cytostatic and cytotoxic by trypan blue dye exclusion tests. Peloruside induced apoptosis in a dose-dependent manner in murine (32D) and human (HL-60) myeloid cell lines, revealed by DNA laddering in agarose gels and flow cytometric analysis of annexin-V- and propidium iodide-stained cells. Treatment of HL-60 cells caused vacuolisation, partial substrate adherence, and the appearance of multi-lobed nuclei, suggesting the induction of a differentiation pathway. Vacuolisation was also observed in a human lung cancer cell line (H441). Opening of the pyranose ring of peloruside by sodium borohydride reduction increased the 48 h IC50 value by 26-fold in 32D cells, suggesting a similar active site to that proposed for bryostatin. However, unlike bryostatin, peloruside failed to bind to PKC in HL-60 cells and was unable to synergize with the calcium ionophore, ionomycin, or with interleukin-2, to activate T-lymphocytes in culture. In summary, although structurally similar to bryostatin, peloruside is a potent inhibitor of cell proliferation, has apoptosis-inducing properties and has a unique mode of action independent of PKC.

Positive selection through a motif in the alphabeta T cell receptor.

The two lineages of T cells, alphabeta and gammadelta, differ in their developmental requirements: only alphabeta T cells require major histocompatibility complex recognition, a process known as positive selection. The alphabeta T cell receptor (TCR), but not its gammadelta counterpart, contains a motif within the alpha-chain connecting peptide domain (alpha-CPM) that has been conserved over the last 500 million years. In transgenic mice expressing an alphabeta TCR lacking the alpha-CPM, thymocytes were blocked in positive selection but could undergo negative selection. Thus, the alpha-CPM seems to participate in the generation of signals required for positive selection.

T cell receptor alpha-chain tail is required for protein kinase C-mediated down-regulation, but not for signaling.

Antigen stimulation through the T cell receptor (TCR) induces phosphorylation of the associated CD3 gamma delta epsilon- and zeta-chain cytoplasmic tails. These events lead to the induction of the intracellular signaling pathways with concomitant receptor down-regulation. The TCR is down-regulated from the cell surface by the activation of protein kinase, C (PKC) and subsequent serine phosphorylation of the CD3 gamma-chain. We report here that the TCR alpha-chain cytoplasmic tail is also necessary for PKC-mediated internalization of the TCR complex. The requirement for the TCR alpha-chain cytoplasmic tail is specific for internalization of the TCR complex, since down-regulation of CD4 is still intact in hybridoma cells expressing a tailless TCR alpha-chain. The absence of TCR internalization directly correlates with defective PKC-mediated phosphorylation of the CD3 gamma-chain. Despite deficient PKC-mediated TCR down-regulation, the tailless alpha beta TCR still transduces antigenic signals resulting in the production of interleukin-2. Although the TCR tails are not obviously required for signal transduction, the TCR alpha-tail may serve as a targeting domain for PKC-mediated down-regulation of the TCR complex.

Signaling efficiency of the T cell receptor controlled by a single amino acid in the beta chain constant region.

A single amino acid residue, Gln136, located within the connecting peptide domain of Cbeta controls the ability of the alpha/beta TCR to transmit a full signal. TCRs in which this Cbeta residue is mutated to Phe, the residue found in TCR-gamma, are unresponsive to antigenic ligands. Interestingly, this Cbeta residue is either polar or charged in every species studied thus far, including the trout and the skate. In contrast, the analogous residue in Cgamma is always hydrophobic. In spite of their compromised antigen responsiveness, the mutant TCR complex contains the CD3-gamma, -delta, -epsilon, and -zeta chains, and undergoes zeta chain phosphorylation and ZAP-70 recruitment. However, the biological response of the mutant TCR could be rescued with a calcium ionophore, implying that mutant TCRs are defective in generating a calcium-mediated signal. The implications of the differences between Cbeta and Cgamma are considered.

A motif within the T cell receptor alpha chain constant region connecting peptide domain controls antigen responsiveness.

Mutant alphabeta TCRs were generated by replacing domains of the alpha and beta chain constant regions with homologous domains from TCR delta and gamma chains, respectively. Chimeric TCRs in which the alpha chain contains TCR delta chain sequences within the connecting peptide domain are unresponsive to alloantigens and superantigens, and have defective interactions with the CD3/zeta complex. Although these antigen-unresponsive TCRs undergo zeta chain phosphorylation upon stimulation with superantigen, they do not generate a full signal capable of producing IL-2. Mutant TCRs acquire signaling activity with a combination of superantigen and calcium ionophore, indicating a defect in calcium-mediated signaling. Finally, a conserved motif, FETDxNLN, present in the alpha chain connecting peptide domain, is disrupted in all signaling-defective TCRs. This conserved alpha chain connecting peptide motif might mediate the transfer of signals from the alphabeta heterodimer to the CD3/zeta complex.

CART: a conserved antigen receptor transmembrane motif.

We have compared the transmembrane sequences of 72 vertebrate antigen receptor (mIg and TCR) polypeptides. This allowed us to identify a Conserved Antigen Receptor Transmembrane (CART) motif which is present in all antigen receptor transmembrane domains from species as far removed as cartilaginous fish. Most of the amino acids in the CART motif are polar or aromatic and may interact with other proteins in the lipid environment. In addition, modeling the antigen receptor transmembrane domain in an alpha helical conformation places the CART residues on one face of the alpha helix. Thus, the CART motif may encode a structural unit which plays a role in the assembly and/or the signaling properties of lymphocyte antigen receptors. We speculate on the potential role of the CART motifs in lymphocyte signaling.

Identification of T cell stimulatory epitopes from the 18 kDa protein of Mycobacterium leprae.

We have used different mouse strains to examine in vivo and in vitro responses to the 18 kDa protein of Mycobacterium leprae, which appears to be strongly immunogenic in both mice and humans. B and T cell stimulatory epitopes recognised by different strains of mice have been mapped using overlapping peptides that span the entire 18 kDa protein. Previous work established that immunization of mice with the 18 kDa protein results in specific antibody production to common B cell epitopes and immunization of mice with peptides containing these B cell epitopes resulted in the induction of specific IgG to only a limited subset of epitopes in each strain. Now we report that T cells purified from mice immunized with peptides that stimulate antibody production, proliferate in vitro when rechallenged. The proliferating T cells produce levels of IL-2 and IFN-gamma, that indicate antigen-specific T helper type 1 cells are present in significant numbers. Thus, a comparison of in vivo and in vitro data suggests that T cells bearing the phenotype associated with potentially protective cell-mediated responses can be primed in vivo by epitopes on small peptides. Since T cells from both strains of mice are capable of responding to the immunogenic synthetic peptides in vitro, but give different responses to the same peptides in vivo, factors other than epitope structure appear to influence T cell subset activation. This may have important implications for diseases such as leprosy where a polarized T cell response appears to develop and for the development of synthetic subunit vaccines.

Genetic control of immune responses to the 18-kDa protein of Mycobacterium leprae. Different TH1 subsets may be involved in proliferative and delayed-type hypersensitivity responses.

In vitro and in vivo responses to the 18-kDa protein of Mycobacterium leprae have been analysed in different strains of mice. Lymphocytes from BALB/cJ (H-2d), BALB.B (H-2b), B10.BR (H-2k), and B10.M (H-2f) mice primed with 18-kDa protein yielded high T cell proliferative responses, while those from C57BL/10J (H-2b) mice yielded lower responses. Both H-2 and non-H-2 genes contributed to the magnitude of responsiveness. F1 mice from high and low responder strains showed high responsiveness to the 18-kDa protein. Supernatants from lymph node cell cultures prepared from 18-kDa protein-immunised BALB/cJ, B10.BR, and C57BL/10J mice contained IL-2 but no IL-4, indicating that activated T cells from both high and low responder mice were of a TH1 phenotype. Cell cultures from low responder C57BL/10J mice produced less IL-2 than those from high responders. The low responsiveness to the 18-kDa protein in proliferative assays might be due to a low frequency of antigen-specific T cells in the C57BL/10J mouse strain. BALB/cJ, C57BL/10J, and F1 (BALB/cJ x B10.BR) mouse strains were tested for in vivo DTH reactions to the 18-kDa protein. All strains, including C57BL/10J, were high DTH responders. Although DTH effector cells and 18-kDa protein-specific proliferative T cells belong to the TH1 subset, our data comparing high and low responder status indicate that distinct TH1 subpopulations are stimulated in response to the 18-kDa protein of M. leprae.

Mapping of T helper cell epitopes by using peptides spanning the 19-kDa protein of Mycobacterium tuberculosis. Evidence for unique and shared epitopes in the stimulation of antibody and delayed-type hypersensitivity responses.

In vivo and in vitro T cell responses to overlapping 20-mer peptides that span the entire 19-kDa protein of Mycobacterium tuberculosis have been compared in three different strains of mice. Immunization of the mice with peptides and analysis of specific antibody production is an in vivo assay of Th cell activity. Peptides 1-20 and 61-80 elicited strong IgG1 responses in BALB/cJ, C57BL/10J, and B10.BR mice, indicating that these peptides could stimulate Th cells, possibly of a Th2 phenotype. T cells isolated from peptide-immunized mice were challenged in vitro with peptide, and their proliferative responses were analyzed. T cells from these three strains of mice immunized with peptides 1-20, 61-80, and 76-95 also responded to challenge with specific peptide in vitro. In addition, B10.BR mice and BALB/cJ mice showed antibody and T cell proliferative responses to peptides 136-155 and 145-159, respectively. Thus, in vitro proliferating T cells were found to possess specificities for peptide epitopes that were almost identical to those of the antibody-producing cells. Delayed-type hypersensitivity (DTH) responses to these peptides were also examined in the three strains. Interestingly, the T cells responding in the DTH assay had Ag specificities that were quite different from those identified in the antibody and proliferation assays. These results suggested that DTH Th cells form a separate population from antibody Th and proliferative T cells and these populations of cells were differentially activated, in an Ag-specific manner.

New generation vaccines: does antibody play a directional role in antigen-processing?

Analyses of recombinant proteins isolated from genomic libraries of pathogenic organisms represent the beginning of identifying immunologically-reactive epitopes. The induction of cell-mediated and humoral immune responses to any pathogen begins with the uptake and processing of antigen by antigen-presenting cells and the display of specific epitopes to the immune system of the host. Little emphasis is placed on the molecular mechanisms underlying transport of foreign proteins into antigen-presenting cells and factors that influence degradation to the peptides which represent the epitopes that associate with newly synthesized class II molecules of the major histocompatibility complex. These cellular processes are crucial to the design of any new generation vaccine. We describe our analysis of the 18 kDa protein antigen of Mycobacterium leprae and consider a possible role for antibody in antigen-processing. In both macrophage/dendritic cells and B lymphocytes, we suggest that antibody plays a directional role in antigen uptake, subcellular compartmentalization, and antigen degradation to yield peptides. These steps will all have an impact on the construction of new generation vaccines.

Immune responses to the 18-kDa protein of Mycobacterium leprae. Similar B cell epitopes but different T cell epitopes seen by inbred strains of mice.

Antibody responses to the 18-kDa protein of Mycobacterium leprae have been analyzed in different strains of mice. High, intermediate, and low responder strains have been identified and these response patterns show clear linkage to genes encoded in the H-2 complex. Three peptides, residues 1-50, 51-100, and 101-148 have been synthesized, as well as a series of 20-mer peptides, which span the entire 18-kDa protein. Repeated immunization of different strains of mice with the 18-kDa protein resulted in IgG responses to epitopes found on all three synthetic peptides. Immunization of BALB/cJ and B10.BR mice, two high responder strains, with 18-kDa protein resulted in high levels of IgG antibody to epitopes found on peptides 1-20, 16-35, 31-50, 46-65, and 76-95. B10.BR mice also contained IgG that bound peptide 61-80 and BALB/cJ mice produced IgG that bound peptide 91-110. Although B10.BR mice produced IgG that bound the 50-mer peptide 101-148, this IgG was not detected by binding to peptides 91-110, 106-125, 121-140, and 131-148. Immunization of B10.BR mice with individual overlapping 20-mer peptides as Ag revealed that peptides 1-20, 16-35, 31-50, and 76-95 elicited high titers of IgG that bound both the immunizing peptide as well as 18-kDa protein. As these peptides induce antibody synthesis they must contain both B cell and T cell epitopes. By contrast, immunization of BALB/cJ mice with the same 20-mer peptides, all of which contain B cell epitopes for this strain, failed to elicit IgG responses with one exception. Peptide 91-110 induced IgG that bound peptide 91-110, but not the intact 18-kDa protein. We conclude that peptides 1-20, 16-35, 31-50, and 76-95 either lack T cell epitopes for BALB/cJ mice, or activate different T cell subpopulations in the two strains. We suggest that the induction of IgG responses to small peptide Ag is an in vivo assay of the activity of Th2 cell subpopulations.

The mapping of epitopes of the 18-kDa protein of Mycobacterium leprae recognized by murine T cells in a proliferation assay.

The 18-kDa protein of Mycobacterium leprae was purified from recombinant plasmids pUL108 and pML-3 grown in Saccharomyces cerevisiae and Escherichia coli, respectively. Significant lymphoproliferative responses were observed when T cells from immunized mice were challenged in culture with purified 18-kDa protein. Synthetic peptides have been prepared that span most of the 148 amino acid residues that constitute the sequence of the 18-kDa protein and used to map epitopes recognized by T cells. When mice were immunized with 18-kDa protein and lymph node cells subsequently prepared and challenged in microculture proliferative assays by using synthetic peptides, only one region of the intact protein appeared stimulatory. This T cell epitope was located between residues 116 and 121, adjacent to an epitope between residues 110 and 115 which we have previously shown to bind the L5 mAb. Immunization of mice with peptides, and subsequent challenge of lymph node cells in assays by using the 18-kDa protein as Ag revealed that residues 111-125 were the most effective in priming responses. Furthermore, the ability of 18-kDa primed lymph node cells to recognize determinants on both M. leprae and Mycobacterium tuberculosis indicates that in addition to possessing an M. leprae-specific B cell determinant, the 18-kDa protein contains a cross-reactive T cell epitope(s).

On the prenatal diagnosis of congenital adrenal hyperplasia (CAH) by measurement of amniotic fluid 17-alpha-hydroxyprogesterone, aldosterone and cortisol.

Forty amniotic fluid samples of both sexes were collected in the 16th gestational week and analysed for 17 alpha-hydroxyprogesterone (17-OHP), cortisol, and aldosterone. Hormone concentrations were also analyzed in amniotic fluid of a male fetus postnatally diagnosed as having the salt-losing form of congenital adrenal hyperplasia (CAH). The mother also had CAH of the non-salt-losing type. Hormone concentrations were also determined prenatally in two pregnancies at risk. Amniotic fluid from the pregnancy with the CAH fetus had an approx. six-fold elevated 17 alpha-hydroxyprogester one level, whereas cortisol and aldosterone levels were within the normal range when compared with controls. Hormone concentrations in the two pregnancies at risk were within normal limits and subsequently a healthy boy and a healthy girl were born. Institution of cortisone in the mother during early pregnancy was made in one of the pregnancies. The treatment was withdrawn when normal amniotic hormonal levels were obtained. No sex difference in concentrations of 17-OHP or cortisol was found in the controls, whereas there was a marked sex difference in aldosterone levels (p less than 0.005) with male fetuses having higher concentrations. Diagnosis of CAH in the 16th gestational week can be made by analysing amniotic fluid concentrations of 17 OHP. As cortisol and aldosterone levels were within normal range of the CAH-fetus, they are probably of little use for the prenatal diagnosis of CAH-fetuses/or to differentiate the simple virilizing and the salt-losing forms of CAH. Restriction fragment length polymorphism (RFLP)- analyses of the 21-hydroxylase gene in the fetus gave little further information.