Structural analysis of a new B-cell-differentiation antigen associated with products of the I-A subregion of the H-2 complex

Human alloreactive CTL interactions with gliomas and with those having upregulated HLA expression from exogenous IFN-gamma or IFN-gamma gene modification

By flow cytometry, a panel of 18 primary glioma cell explants exhibited high expression of class I HLA-A, B, C, but class II HLA-DR expression was absent. Freshly isolated normal brain cells displayed little or no HLA antigens. Alloreactive cytotoxic T lymphocytes (aCTL), sensitized to the HLA of the patient, were generated in a one-way mixed lymphocyte response (MLR). The specificity of aCTL was confirmed to be to target cells (patient glioma cells or lymphoblasts) expressing the relevant HLA antigens. However, nontumor patient-specific aCTL did not lyse normal brain cells. Titration of antibodies to HLA class I into cytotoxicity assays blocked lysis of gliomas by aCTL, confirming aCTL T cell receptor (TCR) interactions with the class I antigen on gliomas. Furthermore, aCTL interactions with glioma cells caused their apoptosis. Coincubations of aCTL with gliomas resulted in upregulated cytokine secretion. Importantly, dexamethasone, an immunosuppressive steroid used for brain edema, did not affect aCTL lytic function against tumor, indicating that steroid-dependent patients may benefit from the immunotherapy. We also explored the use of interferon-gamma (IFN-gamma) to increase aCTL tumor recognition. Coincubation of gliomas with exogenous IFN-gamma (500 U/ml, 48 h) caused a 3-fold upregulation of HLA class I and a slight induction of class II antigen expression. Gene-modified glioma cells producing IFN-gamma similarly displayed upregulated HLA expression. Glioma cells incubated with exogenous IFN-gamma or IFN-gamma-transduced glioma cells were more susceptible to lysis by aCTL than their parental counterparts, thus supporting the concept of combining IFN-gamma cytokine gene therapy with adoptive aCTL immunotherapy for brain tumor treatment.

B cell differentiation antigens as probes for functional B cell subsets

In this review I have discussed the serological, biochemical and functional characterization of two differentiation antigens, Lyb3 and Ia. W39, which have the same time distribution; namely, they are selectively expressed on a late maturing subset of B cells (Lyb3 and Ia. W39) and antigen presenting macrophages (Ia. W39, Lyb3?) Antisera against both determinants were raised in xid defective F1 male mice, which were immunized with spleen cells from the normal parent. Lyb3 is an isogenic specificity expressed without allelic forms in all mouse strains, whereas Ia.W39 is a private specificity, encoded by a gene(s) within the I-Ab subregion of the H-2 complex. Interestingly, the xid gene does not control the synthesis of these differentiation antigens, but affects their membrane expression (shown for Ia. W39.) Lyb3 is a polypeptide of 68,000d MW which has a similar IE point in all mouse strains. The molecule bearing Ia. W39 has an identical 2-chain structure (a and beta) and 2-D gel profile as the molecule expressing all the conventional Ia specificities encoded by the I-Ab subregion. However, from the difference in the ontological appearance and the turnover rate and from sequential immunoprecipitation studies we concluded that there are two kinds of glycoproteins containing Aa and Abeta chains; both would express the conventional specificities, and one would, in addition, bear Ia. W39. Functionally, we have defined Lyb3 as a receptor for triggering signals and Ia. W39 as a specific Ir gene epitope.

Immune response gene function correlates with the expression of an Ia antigen. I. Preferential association of certain Ae and E alpha chains results in a quantitative deficiency in expression of an Ae:E alpha complex

These studies were stimulated by the observation, reported in the accompanying paper (19), that IEu failed to interact with I-Ak or I-As in F1 mice to allow a response to the antigen, pigeon cytochrome c, unlike I-E subregions derived from other Ia.7+ haplotypes. Serological and biochemical analyses were performed to determine whether or not cells from these F1 mice express the Ak,se:E alpha complexes that should function as restriction elements for T cell recognition of pigeon cytochrome c on antigen-presenting cells. Using the Y-17 monoclonal antibody, which recognizes the combinatorial or conformational determinant Ia.m44 on certain Ae:E alpha complexes, we were able to distinguish between Aue:Eu alpha and Ab,k,se:Eu alpha complexes on cell surfaces. Although complement-dependent microcytotoxicity with Y-17 failed to detect Ab,k,se:Eu alpha complexes on cells from appropriate F1 mice, these molecules were detected by both quantitative absorption and quantitative immunofluorescence studies. However, Ab,k,se:Eu alpha complexes were found to be present at levels only one-seventh to one-eighth the levels expressed by homozygous I-Ab, I-Ek; I-Ak, I-Ek; and I-As, I-Ek cells. The results of two-dimensional polyacrylamide gel electrophoresis analyses suggest that the low levels of expression of Ab,k,se:Eu alpha complexes are a consequence of the preferential association of Aue and Eu alpha chains with each other in the F1 cells. As will be shown in the following paper (19), the quantitative deficiency in the expression of Ake:Eu alpha and Ase:Eu alpha complexes results in a corresponding defect in antigen-presenting cell function, thus providing strong evidence that Ia antigens represent products of Ir genes.

Role of Ia. W39 in the interaction of antigen-presenting cells with T and B lymphocytes

Ia. W39 is a B cell differentiation antigen whose membrane expression is controlled by the xid gene. In this report we show that, analogous to its B cell expression, Ia. W39 is also present on a subset of Ia+ macrophages, indicating heterogeneity within that cell population. The Ir gene(s) for the antigenic determinants on the A chain loop of beef insulin maps to the I-Ab subregion of the H-2 complex and, as we have previously reported, is associated with the private specificity Ia. W39. Depletion of Ia. W39+ macrophages eliminates their capacity to present beef insulin to immune T cells, whereas the presentation of the multideterminant antigen trinitrophenylated ovalbumin is reduced less than 50%. Furthermore, we found that H-2b mice lacking Ia. W39+ cells are unable to make a secondary in vivo IgG plaque-forming cell (PFC) response to beef insulin, while the primary IgG PFC response is not dependent on Ia. W39. No shift in the kinetics of the response, nor development of suppressor T cells could be detected in Ia. W39- mice, which would explain their apparent nonresponsiveness to beef insulin after boosting with this antigen. These results, therefore, may reflect a difference in the Ir gene control acting at the primary vs. secondary response level.

Xid-defective male (CBA/N X C57BL/6)F1 accessory cells present bovine insulin to long-term cultured F1-restricted T-cells

The reactivity of H-2b-restricted murine T cells towards bovine insulin was reported to depend on the expression of Ia. W39, a private specificity of I-Ab, on antigen-presenting cells. Cells of male (CBA/N X B6)F1 mice carrying the mutation xid on the X chromosome lack IA. W39 on the cell surface. These cells are unable to present bovine insulin to primed T cells derived from female (CBA/N X B6)F1 mice. We show here that spleen cells of male (CBA/N X B6)F1 hybrids served perfectly as accessory cells for the insulin-dependent induction of a proliferative response of long-term cultured T cells with (B10 X B10.BR)F1 genotype, restricted to recognizing insulin in the context of F1-unique I-A determinants.l The epitope on the insulin molecule essential for stimulation was determined to depend on the glutamic acid residue in position 4 of the A chain of insulin. This contracts with the H-2b-restricted response of B6 mice to bovine insulin, which appears to be directed at the A chain loop determinant (amino acids A8 and A10). These data suggest that distinct I-Ab-encoded structures, the expression of which is regulated independently, may serve as components of restriction elements for H-2b and (H-2b X H-2k)F1 restricted T cells, which are specific for different epitopes of bovine insulin.

Selective loss of antigen-specific Ir gene function in IA mutant B6.C-H-2bm12 is an antigen presenting cell defect

Immune responses to several soluble antigens were compared between B6.C-H-2bm12 mutant and wild-type B6 mice by using a lymph node T-cell proliferation assay. B6.C-H-2bm12 mice failed to respond to beef insulin whereas other IA gene-controlled responses, such as response to poly(L-Tyr, L-Glu)--poly(DL-Ala, L-Lys) and collagen, were indistinguishable between mutant and wild-type mice. The responses to multideterminant antigens such as ovalbumin and purified protein derivative of tuberculin were also found to be comparable in B6.C-H-2bm12 and B6 mice, thus indicating that this mutation resulted in a selective loss of the ability to respond to a certain antigen(s)--e.g., beef insulin. Populations depleted of adherent cells have been used to examine the mechanism by which Ia molecules mediate Ir gene control of antigen recognition. We show that the nonresponsiveness to beef insulin in the mutant mouse is the result of defective antigen presentation. In addition, we find that F1 hybrids between two nonresponders--B6.C-H-2bm12 and B10.A or B10.AKM (IAk) mice--become responders to beef insulin, thus demonstrating gene complementation. These findings taken together with other serologic and biochemical studies in the B6.C-H-2bm12 present convincing genetic evidence for the direct association of the A beta polypeptide chain of the Iab molecules with the expression of immune responsiveness to beef insulin. Study of the B6.C-H-2bm12 mouse should provide new insight into the cellular and molecular mechanisms by which Ir genes determine the nature of the immune response.