INTRASPLENIC VACCINATION AGAINST EXPERIMENTAL MELANOMA

The immunodominant component of a formalinized extracellular antigen ( fECA) vaccine prepared from B16 F10 melanoma cells is the melanoma-ass ociated antigen B700. We now demonstrate that a single prophylactic in trasplenic inoculation of B700 antigen (1-10 mu g) stimulates the prod uction of antibodies which have antiproliferative effects on B16 F10 m elanoma cells in vitro. In addition, potential cytotoxic effects of sp lenocytes from B700 antigen inoculated mice were evaluated for two cel lular immune effector functions, natural killer (NK) cell activity and lymphokine activated killer (LAK) cell activity; both activities were increased following B700 antigen inoculation. Intrasplenic injection of B700 antigen elicited an increase in the expression of the CD25 sur face antigen (IL-2 R alpha) by T lymphocytes and up-regulated the expr ession of IL-2 R alpha mRNA. Thus both humoral and cellular cytotoxic immune responses might play roles in the decreased growth of primary t umors in B700 antigen inoculated mice and in the higher survival rate in this group of animals.