Rinee Mukherjee

CD4+CD25+ regulatory T cells generated in response to insulin B:9-23 peptide prevent adoptive transfer of diabetes by diabetogenic T cells.

NOD mice have a relative deficiency of CD4+CD25+ regulatory T cells that could result in an inability to maintain peripheral tolerance. The aim of this study was to induce the generation of CD4+CD25+ regulatory T cells in response to autoantigens to prevent type 1 diabetes (T1D). We found that immunization of NOD mice with insulin B-chain peptide B:9-23 followed by 72 h in vitro culture with B:9-23 peptide induces generation of CD4+CD25+ regulatory T cells. Route of immunization has a critical role in the generation of these cells. Non-autoimmune mice BALB/c, C57BL/6 and NOR did not show up regulation of CD4+CD25+ regulatory T cells. These cells secreted large amounts of TGF-beta and TNF-alpha with little or no IFN-gamma and IL-10. Adoptive transfer of these CD4+CD25+ regulatory T cells into NOD-SCID mice completely prevented the adoptive transfer of disease by diabetogenic T cells. Although, non-self antigenic OVA (323-339) peptide immunization and in vitro culture with OVA (323-339) peptide does result in up regulation of CD4+CD25+ T cells, these cells did not prevent transfer of diabetes. Our study for the first time identified the generation of antigen-specific CD4+CD25+ regulatory T cells specifically in response to immunization with B:9-23 peptide in NOD mice that are capable of blocking adoptive transfer of diabetes. Our results suggest the possibility of using autoantigens to induce antigen-specific regulatory T cells to prevent and regulate autoimmune diabetes.

Identification of CD4+ T Cell-Specific Epitopes of Islet-Specific Glucose-6-Phosphatase Catalytic Subunit-Related Protein: A Novel β Cell Autoantigen in Type 1 Diabetes

Islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP) has been identified as a novel CD8+ T cell-specific autoantigen in NOD mice. This study was undertaken to identify MHC class II-specific CD4+ T cell epitopes of IGRP. Peptides named P1, P2, P3, P4, P5, P6, and P7 were synthesized by aligning the IGRP protein amino acid sequence with peptide-binding motifs of the NOD MHC class II (I-Ag7) molecule. Peptides P1, P2, P3, and P7 were immunogenic and induced both spontaneous and primed responses. IGRP peptides P1-, P2-, P3-, and P7-induced responses were inhibited by the addition of anti-MHC class II (I-Ag7) Ab, confirming that the response is indeed I-Ag7 restricted. Experiments using purified CD4+ and CD8+ T cells from IGRP peptide-primed mice also showed a predominant CD4+ T cell response with no significant activation of CD8+ T cells. T cells from P1-, P3-, and P7-primed mice secreted both IFN-γ and IL-10 cytokines, whereas P2-primed cells secreted only IFN-γ. Peptides P3 and P7 prevented the development of spontaneous diabetes and delayed adoptive transfer of diabetes. Peptides P1 and P2 delayed the onset of diabetes in both these models. In summary, we have identified two I-Ag7-restricted CD4+ T cell epitopes of IGRP that can modulate and prevent the development of diabetes in NOD mice. These results provide the first evidence on the role of IGRP-specific, MHC class II-restricted CD4+ T cells in disease protection and may help in the development of novel therapies for type 1 diabetes.

Exogenous CLIP localizes into endocytic compartment of cells upon internalization: Implications for antigen presentation by MHC class II molecules

We have previously shown that exogenous CLIP (class II associated invariant chain peptide) downregulated MHC class II expression on antigen presenting cells (APC) and modulated T cell mediated immune responses. The present study was undertaken to investigate the mechanism of uptake of exogenously added CLIP peptide by APC. We found that exogenous CLIP is rapidly internalized by APC and it co-localize with MHC class II in intracellular compartments including early-, late-endosomes and lysosomes. We suggest that exogenous CLIP acts as an in vivo regulator of immune response by internalization and passage through the intracellular compartments where it interferes in peptide loading and recycling of MHC class II molecules to the APC surface. Therefore, exogenous CLIP regulates immune responses by modulation of antigen presentation by the APC.

Identification and purification of a receptor on macrophages for the dengue virus‐induced suppressor cytokine

Dengue type 2 virus (DV)‐induced suppressor cylokine (SF) binds to macrophages to transmit the suppressor signal to recruit the second subpopulation of suppressor T cells. The present study was undertaken to identify and purify the receptor for SF(SF‐R) on macrophages. The binding of 1251‐SF to macrophages was saturable and reversible. Scatchard analysis showed the presence of both high (54 000/cell) and low (178 × 106/cell) affinity receptor sites. The binding of 125I‐SF to macrophages was inhibited by pretreatment of macrophages with anti‐SF antiseruin but not by a heterologous antiserum. Normal mouse peritoneal macrophage membrane was solubilized withTriton‐X‐100 and the components separated by low pressure liquid chromatography (LPLC) to purify SF‐R. The presence of SF binding moiety (SF‐R) was screened at each step of purification. The purified SF‐R resolved into two bands of 45–50 kD mol. wt on SDS‐PAGE. 125I‐SF + SF‐R complex run on SDS‐PAGE showed a single band at about 55–60 kD mol. wt by autoradiography. Anti‐SF‐R anti serum reacted with SF‐R in a Western blot test; the reaction was abolished by pretreatment of the blots with proteinase K, but not by pretreatment with periodic acid. SF‐R was composed of two polypeptide chains (α and β) which were obtained in pure form by high performance liquid chromatography (HPLC) of dithiothreitol‐ and iodoacetamide‐treated SF‐R. Only the β chain bound SK.

Role of TGF-β in Self-Peptide Regulation of Autoimmunity

Transforming growth factor (TGF)-β has been implicated in regulation of the immune system, including autoimmunity. We have found that TGF-β is readily produced by T cells following immunization with self-peptide epitopes that downregulate autoimmune responses in type 1 diabetes (T1D) prone nonobese diabetic (NOD) mice. These include multiple peptide epitopes derived from the islet β-cell antigens GAD65 (GAD65 p202-221, GAD65 p217-236), GAD67 (GAD67 p210-229, GAD67 p225-244), IGRP (IGRP p123-145, IGRP p195-214) and insulin B-chain (Ins. B:9-23) that protected NOD mice from T1D. Immunization of NOD mice with the self-MHC class II I-Ag7 β-chain-derived peptide, I-Aβg7 p54-76 also induced large amounts of TGF-β and also protected these mice from diabetes development. These results indicate that peptides derived from disease related self-antigens and MHC class II molecules primarily induce TGF-β producing regulatory Th3 and Tr1-like cells. TGF-β produced by these cells could enhance the differentiation of induced regulatory iTreg and iTreg17 cells to prevent induction and progression of autoimmune diseases. We therefore suggest that peripheral immune tolerance could be induced and maintained by immunization with self-peptides that induce TGF-β producing T cells.

Surfing the Neuroscience Net

Letters from: [ Pratibha Chaturvedi and Rinee Mukherjee ][1] [ Fred Lenherr ][1] “Surfing the Net” can be confusing if one does not know what to look for or where to look. The recent article by Floyd E. Bloom ([15 Nov., p. 1104][2]) will be helpful to neuroscientists and provides