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Cells from thirty-three human lymphoid cell lines and sublines have been typed for HL-A antigens by a microcytotoxicity test. Similar patterns of HL-A antigens were found for the cell line cells and for the fresh lymphocytes of the donor of the line (eleven cases). However, certain typing sera gave positive reactions with the cell line cells which were not found with the fresh lymphocytes. No correlation was noted between the pattern of these 'extra' reactions and the HL-A typing of the cells. These same typing sera often gave positive reactions with blood lymphocytes cultured for several days in conventional media. These positive reactions were quantitatively more pronounced and sometimes qualitatively different if the cells had been stimulated. A range of normal sera failed to react with cell line cells suggesting that the HL-A typing sera giving 'extra' reactions are detecting antigens in some way related to a histocompatibility system. Absorption studies performed with two of the lines confirmed the HL-A typing by the direct cytotoxicity test. Two sera giving 'extra' reactions were also tested in the absorption experiments. The results indicated that antibodies other than those of the HL-A specificity designated for these sera were responsible for the 'extra' reactions. It is suggested that 'extra' reactions indicate a change in the apparent antigenic expression of lymphoid cells reflecting altered membrane characteristics as they adapt to a culture environment. [ABSTRACT FROM AUTHOR]

This study provides evidence in mice of three strain combinations, that the classical law of transplantation that one gene ⇄ one antigen is applicable. It fails to confirm the suggestion that genic interaction may operate between the histocompatibility loci. [ABSTRACT FROM AUTHOR]

Three instances of third party unresponsiveness in immunologically tolerant mice are reported. Tolerance was induced across the H-2 barrier. Runt disease was prevented by the use of (host × donor) F1 hybrid cells for tolerance induction. The rejection of third party grafts by F1 hybrids from crosses between the host strain and the tolerance inducing donor strain excluded antigenic overlap as a possible explanation for the phenomenon. Third party unresponsiveness was restricted to weak histocompatibility antigens. Skin grafts presenting the tolerant hosts with third party H-2 antigens were rejected with normal promptitude. CBA mice tolerant of A, and A mice tolerant of CBA retained C3H grafts significantly longer than (A × CBA) F1 hosts. It is suggested that this instance of third party unresponsiveness in reciprocally tolerant animals favours the interpretation that the phenomenon is due to incomplete specificity of induced immunological tolerance, rather than to an innate inability of the tolerant hosts to react against the relevant third party histocompatibility antigens. [ABSTRACT FROM AUTHOR]