Cellular basis of anti-SB response.

Cloning of cells allosensitized in vitro against SB1, SB2, and SB3 antigens was performed by micromanipulation. One hundred and twenty-six clones were tested for both proliferative and cytolytic responses; 14 proliferative, noncytotoxic clones and one clone which demonstrated both proliferative and cytotoxic reactivity specific for SB antigens were obtained. The proliferative noncytotoxic clones tested and the clone with both cytotoxic and proliferative activity were all able to produce IL-2-like activity upon specific antigen stimulation in vitro and were positive for OKT3, OKT4 but negative for OKT8. The proliferative clones fit the characteristics of helper T cell (Th) clones while the clone with both cytotoxic and proliferative reactivities is analogous to the class of antigen-driven, helper cell-independent cytotoxic (HITc) clones. No cytolytic nonproliferative SB specific clones were detected. The prevalent induction of Th clones strongly suggests that the biological function of SB antigens is similar to other class II antigens of HLA. The existence of an SB specific HITc clone demonstrates that a determinant on an SB molecule can induce both proliferative and cytolytic responses.