Lack of expression of HLA-ABC antigens in choriocarcinoma and other human tumor cell lines.

We studied a panel of 21 human tumor and other cell lines, mainly of epithelial origin, for the expression of HLA-ABC antigens by an indirect radiobinding assay using monoclonal antibodies. Four of the lines, 2 choriocarcinomas, a breast tumor cell lin (MDA-MB-157), and a colon carcinoma (LoVo) showed no detectable reaction with the antibodies. The levels of binding in another breast tumor line (SkBr3) and a colon carcinoma line (LS174T) were much reduced. These cell lines plus some of the HLA-ABC positive lines from the panel were studied by immunoprecipitation of 35S-labeled cell extracts. Two mechanisms for alteration of the HLA-ABC antigen levels at the cell surface were apparent. In the choriocarcinomas and one breast tumor line, beta 2 microglobulin (beta 2m) was expressed but little or no HLA-A, B, or C polypeptides were synthesized. The other HLA-ABC negative lines had defects similar to that in the previously reported Burkitt's lymphoma cell line DAUDI. In these lines, HLA-ABC polypeptides were produced but did not appear at the cell surface because beta 2m was not synthesized. The absence of HLA-ABC determinants from the cell surface is presumed to afford protection against T-cell immune attack whether naturally as against the trophoblast during pregnancy or in abnormal situations against certain tumors.