Biological response modifier as antigen: OK432-specific T-cell clone as an anti-tumor effector cell.

OK432, a Streptococcus preparation, is a biological response modifier that has been used in the treatment of malignant diseases. A cloned Thy 1.2+, L3T4+, Lyt 2.2- T cell (OK2.21), specific for OK432 and restricted to I-Ed, was isolated from BALB/c mice immunized with OK432. OK2.21 not only secreted interleukin 2 but also killed Iad-bearing B-lymphoma cells in an antigen-specific manner. The clone also killed Ia-negative bystander tumor targets, but only in the presence of both OK432 and antigen-presenting cells. Despite the cytotoxicity against tumor cells, OK2.21 did not kill OK432-pulsed normal spleen cells. Injection of this clone together with OK432 to tumor-bearing BALB/c mice prolonged their survival, suggesting that this clone acts as an anti-tumor effector (or effector-inducer) cell in the therapy with OK432.