The protective effect of antisera against leukaemia in vivo--a reappraisal.

The ability of antibody to co-operate with certain non-immune lymphoid cells in the rejection of tumours has been studied both and . Anti-serum raised in rabbits against a PVGc rat leukosis can be rendered “tumour specific” by absorption in normal PVGc rats and this antiserum can be shown to have lymphocyte dependent antibody (LDA) activity against the tumour cell . Complement lytic activity of the antiserum is weak or absent against the tumour. Passive administration of the antiserum to rats protects the animals against the development of leukaemia. Maximum protection occurs if the anti-serum is given before the tumour inoculum and is less effective given after the tumour inoculum. No protective effect can be demonstrated with “tumour specific” allo-antisera or syngeneic antisera against the tumour and no LDA activity can be detected against the tumour in vitro. Good correlation exists between LDA activity in the sera of the recipients and the protective effect. The results are discussed in terms of the kinetics of cell killing after models described for killing by chemotherapeutic agents in animals.