Apparent alteration in MHC antigens in K36.16, an AKR thymoma, does not result in genetic rearrangement.

An 'alien' MHC antigen has been previously described in the AKR tumour K36.16. We have attempted to establish the nature of this antigen by immunochemical techniques. Sequential immunoprecipitation and affinity purification of the 'alien' and regular antigens show that the same molecular entity is involved, the H-2Kd molecule being precipitated by anti H-2Dd sera. Absorption of the sera used to define this 'alien' antigen suggests that an interaction between endogenous viral antigens and H-2 is responsible. Genetic rearrangement within the MHC may well be a facet of tumour immunology but the AKR tumour K36.16 does not appear to be a suitable example for further study.