Dissection of macrophage tumoricidal and protozoacidal activities using T-cell hybridomas and recombinant lymphokines

Macrophage (MΦ) phenotype and function can be modified by various T-cell lymphokines (LK). The alteration of MΦ phenotype is a result of LK concentration, duration of exposure, and the level of MΦ activation when obtained from in vivo sources through elicitation by either sterile irritants or cellular immune mechanisms. To dissect MΦ activation into discrete signals, we constructed T-cell hybridomas by fusing hypoxanthine-aminopterin-thymidine-sensitive BW5147 cells with nylon wool-purified, concanavalin A-stimulated T cells. The resulting T-cell hybrids were screened for their ability to (1) protect MΦ from the cytopathic effect of Naegleria lysates, (2) induce class II major histocompatibility complex gene product (Ia antigen) expression, (3) increase tumoricidal and cytostatic activity, and (4) alter ectoenzyme profiles on either resident or thioglycolate-elicited MΦ. Two hybridomas (T-3 and T-9) were selected for further evaluation because of their activity patterns. Supernatants from T-3 and T-9 were compared with cloned gamma-interferon (IFN-γ) for alterations of biological activities. Both T-3 and T-9 were able to protect resident-MΦ cells from Naegleria lysate but had no protective effect on thioglycolate-induced MΦ. T-9 supernatant had patterns of activity similar to IFN-γ, whereas T-3 patterns were different. The addition of anti-IFN-γ removed T-9 cytostatic activity while not affecting T-3-induced activity. The LK inducing protection from the cytopathic effect of Naegleria lysate is not IFN-γ but another molecular moiety. We conclude that the activation of MΦ for the destruction of tumor cells and amoebae may occur via different mechanisms.