IMMUNOLOGICAL PARADOX IN TESTICULAR-TUMORS - THE PRESENCE OF A LARGE NUMBER OF ACTIVATED T-CELLS DESPITE THE COMPLETE ABSENCE OF MHC ANTIGENS

Tissue sections from 22 seminoma (Se) and 10 teratoma (Te) patients we re investigated for correlation between the presence of tumour infiltr ating T-lymphocytes (TIL) and the expression of major histocompatibili ty complex (MHC) antigens using an immunoperoxidase staining technique . Complete absence of both class I and II antigens was observed in all Te and 20 out of 22 Se. The two positive Se showed only weak expressi on on 2% of tumour cells. Despite the absence of human leucocyte antig ens (HLA) there were a large number of TIL scattered throughout the ti ssues in the case of Se with no predominance of CD4 or CD8 subpopulati ons in either group. Tgamma positive cells were less than 5% of total CD3 positive cells in both Se and Te. The majority of the TIL were fou nd to express activation markers, i.e. HLA class II antigens. Culture of tumour cell suspension with IL-2 produced passageable IL-2-dependen t T cells from 10 out of 15 tumours. Studies with testis cell lines sh owed the complete absence of class I antigens in 2 out of 5 cases and the inability of interferon gamma (IFN gamma) to induce expression. IF N gamma also failed to induce class II antigens in three out of five o f these lines. The immunological paradox of the presence of a large nu mber of activated T-cells in testicular tumours despite the complete a bsence of MHC antigens remains unexplained and needs further investiga tion. Possible hypotheses are reviewed.