Determinant-specific regulation of T helper cell responses to murine lambda light chains by both H-2 and non-H-2 genes

Processing and presentation of idiotypes to MHC-restricted T cells

Among the self antigens, immunoglobulins, and in particular idiotypes, are of special interest because of their extreme sequence heterogeneity and their postulated involvement in regulatory interactions in the immune system. We have therefore studied antigen processing and presentation of variable region peptides, processed idiotypes, to MHC class II molecule-restricted T cells. The immunoglobulin used has been the lambda 2(315) light chain produced by the BALB/c MOPC 315 plasmacytoma (alpha, lambda 2). The minimum length of a stimulatory synthetic idiotypic peptide comprises residues 91-101 of lambda 2(315) and is presented by the I-E(d) molecule to CD4+ T cells. T cell clones with specificity for the 91-101(lambda 2(315))/I-E(d) complex utilize a limited TCR repertoire and are of both Th1 and Th2 type. For presentation, extracellular lambda 2(315) requires endocytosis and processing, as previously described for conventional exogenous antigens. In addition, a B lymphoma cell can process and present its own endogenous lambda 2(315). This was shown by transfecting manipulated lambda 2(315) gene variants into B lymphoma cells, followed by evaluation of the APC function of the transfectants. These studies demonstrated that surface expression or secretion of lambda 2(315) is not necessary for presentation and suggested that the endoplasmic reticulum may be a processing compartment. To extend our findings to naive Id+ B cells and anti-Id T cells, we have generated lambda 2(315)-transgenic as well as TCR-transgenic mice. A model is presented for a T-B cell interaction based on presentation of processed idiotypes.

Relative susceptibility of SJL/J and B10.S mice to experimental allergic encephalomyelitis is correlated with high and low responsiveness to myelin basic protein

SJL/J mice are highly susceptible to actively induced experimental allergic encephalomyelitis (EAE), whereas B10.S mice are not. Yet both strains share the H-2s major histocompatibility complex (MHC) haplotype. In order to help determine the cellular basis for the disparate susceptibility to EAE, the antigen-specific in vitro proliferative responses of lymph node (LN) T cells from SJL/J and B10.S mice primed with porcine myelin basic protein (MBP) were assessed. The results indicated that SJL/J mice were high responders and B10.S mice were low responders to both porcine and murine MBP, as demonstrated by limiting dilution analyses and cloning efficiency analysis of MBP-reactive T cells. The low response of B10.S mice to MBP was not due to elevated suppressor cell activity or to a discernible defect in antigen-presenting cell activity. Rather, it appeared to be due to a paucity (or defect in function) of high affinity MBP-reactive T cells in B10.S as compared to SJL/J mice. This difference in MBP responsiveness must, by necessity, be linked to non-MHC background genes. Therefore, assuming that the relative number of MBP-reactive T cells parallels that of EAE-effector T cells in SJL/J and B10.S mice (as separate in vivo studies indicate), the present results suggest that differences in the T cell repertoire for the encephalitogenic determinants of MBP may contribute significantly to the observed differences in antigen reactivity, and may relate to differences in susceptibility to EAE.

Dominant suppressive effect of the silent Eb alpha allele on an in vivo T helper cell response under Ed beta Ed alpha region-linked immune response gene control

Previous adoptive spleen cell transfer experiments have demonstrated that an immune response (Ir) gene linked to the Ed beta Ed alpha region allows BALB/c T helper lymphocytes (Th) to respond to an idiotope on the V lambda 2(315) fragment of isologous myeloma protein M315. BALB.K (H-2k) and BALB.B (H-2b) do not respond to V lambda 2(315). While (H-2d X H-2k)F1 hybrids have been shown to be responders, it is now demonstrated that (H-2d X H-2b)F1 hybrids are low responders. By crossing BALB/c with various H-2 recombinants on B10 background and probing Th responsiveness to V lambda 2(315) in these F1 hybrids, the dominant suppressive gene of the H-2b haplotype is mapped to Eb alpha Sb. It is argued that the suppressive gene is Eb alpha, which is a silent allele. A likely explanation for the suppressive effect of the Eb alpha allele is that reduced amounts of Ed beta: Ed alpha restriction elements are present on antigen-presenting cells of (H-2d X H-2b)F1 hybrids because only one E alpha gene is functional in such mice. The present report extends previous in vitro findings from other laboratories to the in vivo situation and suggests that silent alleles for class II molecule chains may profoundly affect certain immune responses of individuals heterozygous for the silent allele.

Antibody responses to lambda 1J558 and lambda 2315 light chains. Specificity and genetic regulation

Specificity of BALB/c antibody responses to lambda chains of isologous myeloma proteins 315 and J558 was explored by enzyme-linked immunosorbent assay. lambda-chain binding antibodies were not detected when immunizing with assembled (H + L) myeloma proteins. However, relatively high titred IgG antibodies were elicited by free lambda 2(315) immunization. Antibodies were directed to 'hidden' determinants since binding was abrogated upon H + L assembly of chains. At least a portion of antibodies bound antigenic determinants in the variable region and cross-reacted with lambda 1 land lambda 3 chains. Free lambda 1J558 immunization induced low-titred, predominantly IgM antibodies that also only reacted with 'hidden' determinants. These determinants were most probably located in the constant (C) region and no cross-reaction to lambda 2 or lambda 3 was observed. An artefact of technical importance was noted: myeloma proteins exposed 'hidden' determinants on their lambda chains when coated directly to polystyrene walls. This artefactual exposition was lost when anti C-region antibody spacer molecules were inserted between the wall and the myeloma proteins. Antibody and T helper cell (Th) responses to free lambda 2(315) covaried significantly in various strains while antibody and Th responses to free lambda 1J558 did not. In some strains, weak antibody responses were detected without detectable Th.

Specificity of antibody and helper T-cell responses to the isologous myeloma protein W3129 and its subunits

The specificity of BALB/c antibodies and Th elicited by BALB/c myeloma protein W3129 (alpha, kappa) and its subunits was studied. Antibodies were detected with RIA and ELISA techniques. Th were demonstrated by their ability to augment a secondary anti-NIP antibody response in a Mitchison type assay of adoptive immunity. The major proportion of antibodies elicited by the complete W3129 was directed to an idiotypic determinant(s) that depended on assembled H + L chains. The determinant(s) was probably located in or near the antibody combining site because binding was hapten-inhibitable. A second minor antibody population bound an idiotypic determinant(s) on VW3129H expressed on isolated H-chain as well as on the complete myeloma protein. A third and very weakly reactive set of antibodies was specific for a C alpha antigenic site(s) which was expressed much more efficiently on free than on assembled alpha-chains. The antibody response to free kappa W3129 was directed to idiotypic determinants that were inaccessible in the complete molecule. By contrast, free kappa W3129 elicited Th that responded to an idiotypic determinant(s) on VW3129K; the determinant(s) was expressed on both the isolated chain and the complete W3129, suggesting that Th responded to an idiotope not recognized by B-cells. Priming with free alpha W3129 failed in four out of five experiments to induce Th that responded to the complete W3129, demonstrating that a major difference existed between VH and VL of W3129 regarding their immunogenicity for Th. Nevertheless, free alpha W3129 did elicit antibody responses that displayed high reactivity with the complete molecule, indicating that certain serologically defined antigenic sites on the surface of W3129 are also expressed on isolated alpha W3129. Thus, certain differences were detected as to the specificities of Th and B-cells for W3129 and its subunits since they recognized separate idiotopes located in the VL- or VH-region, respectively. The pattern of Th recognition of W3129 resembled that of another isologous myeloma protein, M315, but was unlike that of a third, J558, previously described from this laboratory.