Specificity of antigen binding by T cells; competition between soluble and Ia-associated antigen

Expression of MHC class II antigens in human lung cancer cells

Surgical specimens of lung cancers were examined immunopathologically for the expression of major histocompatibility complex class II (MHC-II) antigens in the tumor cells and their relationship to the lymphocytic infiltration. A lymphocytic infiltrate was frequently observed in the tumor tissue, though its intensity differed among the various histological types. MHC-II antigens were often demonstrated in tumors with a lymphocytic infiltrate. They were detected predominantly in the cytoplasm of tumor cells and to a lesser extent on the cell membranes. The emergence of the MHC-II-positive tumor cells was closely related to a local infiltration by lymphocytes including interferon-gamma (IFN-gamma)-producing T-cells. On the basis of the histological findings, an in vitro experiment was carried out. Four types of lung cancer cells were incubated with recombinant IFN-gamma in order to induce MHC-II antigens. MHC-II antigens (HLA-DR as well as HLA-DQ and HLA-DP antigens) were elicited in three cancer cell lines depending on the concentration of IFN-gamma. Immunoelectron microscopic study revealed that they were expressed on the surface of the cell membrane, though to a lesser extent than in the cytoplasm. It was considered that MHC-II antigens could be induced in some tumor cells in the immunological environment where IFN-gamma was secreted from T-cells and concentrated locally.

Suppression of avidin processing and presentation by mouse macrophages after sublethal exposure to dieldrin

The molecular events in macrophage antigen processing and presentation were examined to determine the possible site(s) of cell-xenobiotic interaction. Antigenic processing by mouse peritoneal macrophages of a single protein antigen, avidin, was significantly suppressed following sublethal exposure of animals to an organochlorine pesticide, dieldrin. Exposure of C57B1/6 female mice to dieldrin affected the in vitro uptake of [methyl-14C]avidin by peritoneal macrophages and markedly decreased phagocytosis of fluorescein-labelled microspheres and Salmonella typhimurium. Release of the processed avidin, determined by immunochemical quantification of immunogenic avidin and by bioassay of immunogenicity of the released antigen, was also markedly affected. Dieldrin markedly affected presentation of avidin on the macrophage surface, observed by cytoimmunochemical staining of the antigen with fluorescent antibody and flow cytometry. Inhibition of the release of processed avidin was dieldrin dose- and time-dependent, following single sublethal intraperitoneal (ip) exposure to the pesticide. The antigenic properties of processed avidin, determined by biological assay using lymphocyte cultures of normal C57B1/6 mice primed with avidin, were proportional to the antigen concentration in supernatants of macrophage cultures, for both vehicle controls and dieldrin-exposed animals. This observation and analysis of the kinetics of release of processed avidin by macrophages from control and dieldrin-exposed animals suggested that the release of processed avidin, but not the immunogenicity of the antigen itself, was affected by the pesticide exposure. Generally, impairment of avidin processing and presentation appeared to be more dramatic than other pesticide-related injuries to macrophages, such as the uptake of the antigen. In conclusion, antigen processing could be a sensitive target for dieldrin-related injury of macrophage functional activities, which, in consequence, could produce suppression of the humoral immune response.

Quantitation of MHC antigen expression on colorectal tumours and its association with tumour progression

A flow cytometric technique has been established for accurately quantitating the cell surface density of MHC antigens and the percentage of cells expressing MHC antigens in 38 colorectal tumours. Thirty-four percent of tumours were partially or completely negative for HLA-ABC antigen expression. Although the quantity of HLA-ABC antigens varied widely, there was no correlation between the density of HLA-ABC antigens, or the percentage of cells expressing these antigens and clinicopathological stage. Fifty percent of the colorectal tumours expressed HLA-DR with varying antigen densities. All of the poorly differentiated tumours expressed HLA-DR but there was no correlation between expression of HLA-DR and clinicopathological stage. The aneuploid tumours expressed more HLA-ABC and HLA-DR antigens on a higher percentage of cells than the diploid tumours. Abnormal expression of the tumour associated antigens CEA, Y haptenic blood group and 791T p72 also correlated with expression of HLA-ABC and HLA-DR antigens on colorectal tumours. The majority of early derived in vitro dividing cells failed to express both HLA-ABC and HLA-DR antigens although they expressed high levels of tumour associated antigens. If there is a correlation between in vitro and in vivo growth perhaps tumours are maintained and seeded by MHC antigen negative cells.

Antigenic requirements for T-cell activation: reconstitution of a functional antigen from an inactive peptide portion of an antigen conjugated to protein carriers

The structural features of an antigenic peptide required for T-cell activation were examined by a novel approach: an active antigen was constructed from an inactive peptide portion of the original antigen by conjugating it to various proteins. An eicosapeptide, peptide 8, representing residues 103-112 of the tobacco mosaic virus protein (TMVP), was utilized as the model antigen for these studies. While peptide 8 was able to stimulate, in vitro, T-cells from peptide 8 primed mice, synthetic peptides representing various portions of peptide 8 were unable to activate these cells. Although the amino-terminal undecapeptide of peptide 8 (residues 93-103 of TMVP) was unable to activate T-cells from peptide 8 primed mice, conjugates which consisted of this undecapeptide coupled to certain proteins were capable of inducing antigen-specific proliferation of these T-cells. These results identify two structural antigenic features essential for T-cell activation: a T-cell-recognizable epitope within the amino-terminal undecapeptide of peptide 8 and a second region provided by the carboxy-terminal half of peptide 8 or by protein carriers. Potential roles for this second region include providing a site for antigen interaction with Ia molecules on the antigen-presenting cell or, alternatively, providing amino acids important in stabilizing the binding of the T-cell antigen receptor. The results suggest that the recognition of this second region exhibits only a limited specificity.

Antigen-specific helper factor production by immortalized clone of OVA-specific T cells. I. In vitro activity

Immortalized clones of virally transformed OVA-specific T cells produce antigen-specific helper factor upon stimulation in vitro. The helper factor activate DNP-primed B cells to multiply and synthesize IgG anti-DNP antibodies. The trigger of the helper clone is antigen specific and the B cell-stimulating hapten must be coupled to the specific T cell carrier in order to transfer the help signal from the activated T clone to the B lymphocytes. Activation of the helper clone is performed by antigen-pulsed macrophages and cannot be achieved by the free soluble antigen. However, cell-free supernatant of the antigen-pulsed macrophages can stimulate the helper cells. Thus the antigenic determinant must be presented to the helper cell in the form of macrophage-processed antigen. These requirements for antigenic stimulation and the activity of the secreted helper factor demonstrate that the immortalized helper clone preserved the cellular components which control the antigen-specific immune function of the normal T lymphocyte.

Flow cytometric analysis of specific binding of soluble Ia by I-region restricted alloactivated T cells

An antigen binding assay has been developed for quantitation by flow cytometry of vesicular and soluble Ia binding by alloactivated T cells. Binding of stimulator membrane vesicles was detected by anti-Ly-6.2 or anti-Ia monoclonal antibodies coupled to fluorescent latex beads. Vesicle binding by an I-Ak specific A.TH anti-A.TL T cell line occurred via I-Ak molecules, in that (a) vesicles expressing I-Ak molecules bound much more effectively than vesicles of H-2b,q strains, and (b) inhibition of H-2k vesicle binding occurred with anti-I-Ak, but not anti-Kk, anti-Ek, or anti-Dk antibodies. T cell receptor/Ia interactions were directly studied by inhibition of H-2k vesicle binding by T cells with partially purified Ia glycoproteins. Inhibition of binding occurred via Ia molecules since (a) affinity column partially purified allogeneic I-Ak molecules inhibited binding much more effectively than syngeneic I-As molecules and (b) depletion of I-Ak but not Ek molecules in Iak containing glycoprotein fractions abrogated the inhibitory effect. The ability of this method to detect specific binding of soluble Ia with antigen activated T cells makes it a useful tool for studying interaction of membrane free major histocompatibility complex (MHC) products with native T cell receptor.

Receptor specificity of Ia-restricted T lymphoblasts activated against trinitrobenzene sulfonate-coupled spleen cells: recognition of distinct trinitrophenyl and Ia moieties

The receptor specificity of H-2-restricted T lymphoblasts activated against trinitrobenzene sulfonate (TNBS)-coupled spleen cells was examined using an antigen binding assay. A population of Lyt-1+,2-T lymphoblasts acquired syngeneic Ia determinants during 4 days of primary culture with hapten-coupled stimulator cells. Syngeneic Ia was not reexpressed after trypsin treatment of the T cells, but was found after incubation with soluble Ia shed from lipopolysaccharide-activated blasts. Self-Ia binding was specific in that Lyt-1+,2- but not Lyt-1-,2+ cells acquired the antigen, and in that self-Ia bound more effectively than allogeneic Ia material. To determine the relationship of self-Ia binding to the recognition of foreign antigen, the binding of trinitrophenyl (TNP)-coupled plasma membrane vesicles by TNP-specific T cells was studied. TNP-vesicle binding occurred via TNP and H-2(Ia) molecules on the vesicles in that binding was inhibited with antibodies against TNP or H-2(Ia) molecules but not non-major histocompatibility complex (e.g., Ly-6.2) molecules on the vesicles. Complete inhibition of TNP-vesicle binding by an Iak-restricted TNP-specific T-cell line occurred with soluble TNP-lysine, but not an unrelated hapten, N-iodoacetyl-N-(5-sulfonic-1-naphthyl)ethylenediamine (I-AED)-cysteine. Conversely, I-AED-cysteine, but not TNP-lysine, inhibited binding of I-AED-coupled B6 vesicles by B6 anti-I-AED T cells. Significant, but weak inhibition of TNP-vesicle binding by the anti-TNP line was observed with glycoprotein preparations containing partially purified self-Ia molecules. However, inhibition was specific for I-Ak molecules, in that inhibition was lost after removal of I-Ak molecules from the glycoprotein preparation, and very little inhibition occurred with soluble glycoproteins prepared from thymocytes which contained very little Ia material or from LPS blasts of an unrelated H-2 haplotype. These results suggest a recognition model in which TNP and Ia determinants are recognized by neighboring receptor combining sites.

Expression of major histocompatibility antigens and leucocyte infiltration in benign and malignant human breast disease

The reactivity of murine monoclonal antibodies (McAbs) directed against the monomorphic determinants of Class I and Class II antigens of the major histocompatibility complex (MHC), and against antigens expressed by discrete populations of leucocytes was studied using the indirect immunoperoxidase technique on serial tissue sections of 16 benign and 17 malignant primary human breast tumours. Class I antigens (detected by the McAb 2A1) were consistently associated with stromal leucocytes, fibroblasts and vascular endothelium, but expression on epithelial cells particularly of malignant provenance, was more variable. Class II antigens (detected by TDR 31.1) were present upon a variety of cell types which also included sporadic expression on malignant and benign epithelia. The distribution of leucocytes grossly monitored with 2D1 (reactive with a common leucocyte antigen) was largely interepithelial and periductal in benign lesions. Leucocytes were generally more numerous in malignant tumours, where they were largely confined to the stroma. The majority (approximately 75%) of leucocytes were T lymphocytes (reactive with UCHT1), some of which appeared to react with TDR 31.1 and were therefore activated. Ratios of helper/inducer (OKT4+) and suppressor/cytotoxic (OKT8+) subsets generally exceeded unity in malignant neoplasms. There was no correlation between the extent and distribution of T cells and the HLA status of the epithelial cells. Leucocytes detected by the monoclonal antibody OKM1 which reacts with monocytes/macrophages, granulocytes and large granular lymphocytes were numerically few and again mainly confined to the stroma. In a limited number of tests, leucocytes detected with HNKl, reactive with a differentiation antigen expressed on some cells which mediate natural and antibody-dependent cellular cytotoxicity in vitro although detectable interepithelially in benign tumours, were virtually absent from malignant tissue. HNK1 also cross-reacted with myoepithelial cells in the ducts of benign lesions.

The membrane antigens of human colorectal cancer cells: demonstration with monoclonal antibodies of heterogeneity within and between tumours and of anomalous expression of HLA-DR

The membrane antigens of fifteen colorectal tumours were studied using a number of monoclonal antibodies and the immunoperoxidase technique on frozen sections. With this approach we could easily demonstrate differences in the membrane structure of the cancer cells within the tumour mass of given patients and also readily demonstrate differences between tumours that were indistinguishable by histological and other standard criteria. An unexpected finding was the patchy expression of HLA-DR antigens on cancer cells, in spite of the absence of HLA-DR on normal colorectal epithelium. These findings have interesting theoretical and clinical implications.

Molecular events in the processing of avidin by antigen-presenting cells (APC). III. Activation of T-lymphocyte lines and H-2 restriction are mediated by processed avidin associated with I-region gene products

We investigated the interaction between processed avidin (PA) and avidin-specific lines of T lymphocytes free of resident antigen-presenting cells (APC). We found that PA was able to replace the requirement for APC in the T-lymphocyte proliferative assay, only if the PA was associated with an Ia-positive moiety (IPM) supplied by the APC. In addition to supplying a necessary signal for a proliferative response to PA, IPM imposed H-2 restriction on the PA molecule. The association between PA and IPM was reversible and the two moieties could be physically separated and recombined. The results support a conclusion that major histocompatibility restriction of the interaction between T lymphocytes and APC is due to the association between processed antigen and an APC element containing I-region products.

Molecular events in the processing of avidin by antigen-presenting cells (APC). II. Identical processing by APC of H-2 high- and low-responder mouse strains

The differences between the immune response (Ir) phenotypes of H-2 gene-controlled high- and low-responder mice have been attributed to events occurring at the interaction between antigen-presenting cells (APC) and lymphocytes. To investigate this interaction we undertook a study of molecular events in the processing of avidin, a molecule whose uniquely strong affinity for binding to biotin renders it traceable at very low concentrations, and a molecule to which the T-lymphocyte immune response is controlled by Ir genes. In this paper we describe the generation of processed avidin by APC and characterize it biochemically and immunologically. We found that APC of H-2 genetically high- and low-responder mice were indistinguishable in their capacity to generate immunogenic processed avidin (PA). Immunogenic PA differed from native avidin in size and carbohydrate moieties, but preserved its capacity to bind biotin, and was 1000-fold more efficient than NA as an immunogen for primed T lymphocytes. Primed T lymphocytes appeared to recognize PA that was conformationally intact. Highly immunogenic PA was not H-2 restricted. Thus, differences in the Ir phenotype of the response to avidin could not be attributed to determinant selection by APC.