MHC class I expression by developmental tumors: teratocarcinoma stem cells are TCA positive

We have investigated the expression of antigens recognized by several alloantisera and monoclonal antibodies to class I and class I-like MHC gene products on four developmental tumor cell lines derived from teratocarcinoma and choriocarcinoma. The analysis by cytotoxicity, immunoprecipitation, and Northern blotting analysis was also performed following treatment of the cells with gamma interferon. Three of four of the cell lines apparently do not express polymorphic determinants of HLA-A,B,C class I MHC genes. Immunoprecipitation with antibodies to HLA monomorphic determinants or beta 2m showed that some cell lines express distinct novel class I MHC-like molecules; the latter show molecular sizes different from regular HLA molecules and are associated with beta 2m. The Northern blotting showed class I mRNA present in three out of four of the developmental tumor cell lines but at at least tenfold lower levels than in lymphoid cells; it is possible that the RNAs homologous to class I DNA probes include transcripts of non-HLA-A,B,C genes. The cells were serologically typed for one such locus, TCA, which lies telomeric to HLA-A; the choriocarcinomas are negative and the teratocarcinomas are positive. The relationship between the different antigenic molecules and their possible functional significance is discussed in terms of maternofetal interactions, cancer, and transplantation.