[Changes in the expression of H-2 antigenic determinants in several sublines proceeding from the same tumor]

Four sublines of the chemically induced BALB/c tumour MCG4 have been obtained after serial intraperitoneal transplantation in syngeneic recipients and have been named MCG4-O, MCG4-A, MCG4-B and MCG4-C. The four subline have been typed for H-2 antigens in a complement dependent microradioassay with H-2 alloantisera defining H-2 specificities as well as with two syngeneic anti tumour sera: BALB/c anti MCG4-O and BALB/c anti MCG4-A. The results obtained showed a progressive loss of the foreign H-2 antigens detected in the primitive line, MCG4-O, with a simultaneous appearance of the appropriate H-2 antigens detected in MCG4-B and MCG4-C. Furthermore the immunogenic capacity of the sublines decrease progressively with the transplantation procedures, rendering MCG4-O and MCG4-A highly immunogenic and capable of producing isoantibodies while MCG4-B and MCG4-C are poorly immunogenic. The results could suggest that the primitive subline is heterogeneous mixture of (H-2d) are immunoselected by the transplantation procedures with rejection of the most immunogenic clones, which would express the foreign H-2 antigens.