Novel tumor-specific antigen(s) response observed in a syngeneic lymphoma-bearing host.

Immunoglobin (Ig) has been found to accumulate on P815Y (H-2d) and L5178Y (H-2d) tumor cells during progressive growth in syngeneic host DBA/2 mice. Density of the accumulated Ig per cell increases as the tumor grows while the tumor cells become resistant to lysis by ascitic syngeneic cytotoxic cells. Tumor cells grown in vivo coated with this specific Ig no longer bind significant amounts of antibodies against H-2D and H-2K antigens. The membrane-bound Ig reacts with a rabbit antimouse Fab and a rabbit antimouse IgM reagent, but it does not react with a rabbit antimouse IgG or IgA reagent. It binds specifically to tumor cell lines that are sensitive to the ascitic cytotoxic cells but not to resistant tumor cell lines. The membrane-bound Ig can be eluted from tumor cells with 3 M NaSCN or 0.2 M acetic acid. Binding studies indicate that this eluted Ig is not an anti-H-2D/K antibody, yet it immunoprecipitates H-2D/K antigens from NP40 lysates of P815Y cells. It is proposed that the Ig is directed against a tumor antigen that is physically associated with the H-2D/K antigens of the tumors.