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Dissection of macrophage tumoricidal and protozoacidal activities using T-cell hybridomas and recombinant lymphokines
Abstract:
Macrophage (M phi) phenotype and function can be modulated by various T-cell lymphokines (LK). The alteration of M phi phenotype is a result of LK concentration, duration of exposure, and the level of M phi activation when obtained from in vivo sources through elicitation by either sterile irritants or cellular immune mechanisms. To dissect M phi 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 (i) protect M phi from the cytopathic effect of Naegleria lysates, (ii) induce class II major histocompatibility complex gene product (Ia antigen) expression, (iii) increase tumoricidal and cytostatic activity, and (iv) alter ectoenzyme profiles on either resident or thioglycolate-elicited M phi. 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-gamma) for alterations of biological activities. Both T-3 and T-9 were able to protect resident-M phi cells from Naegleria lysate but had no protective effect on thioglycolate-induced M phi. T-9 supernatant had patterns of activity similar to IFN-gamma, whereas T-3 patterns were different. The addition of anti- IFN-gamma 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-gamma but another molecular moiety. We conclude that the activation of M phi for the destruction of tumor cells and amoebae may occur via different mechanisms.
Insights
T-cell hybridomas revealed distinct macrophage (M phi) activation signals. One signal, similar to gamma-interferon (IFN-gamma), protects against Naegleria lysates, while another, distinct signal, activates M phi for tumor cell destruction.
Area of Science:
- Immunology
- Cell Biology
Background:
- Macrophage (M phi) function is modulated by T-cell lymphokines (LK).
- M phi phenotype alterations depend on LK concentration, exposure duration, and activation levels.
- Dissecting M phi activation requires isolating discrete signaling pathways.
Purpose of the Study:
- To construct and screen T-cell hybridomas for lymphokine production that differentially activate macrophages.
- To investigate the specific signals involved in macrophage activation against pathogens and tumor cells.
Main Methods:
- T-cell hybridomas were generated by fusing BW5147 cells with activated T cells.
- Hybridoma supernatants were screened for effects on macrophage protection, Ia antigen expression, tumoricidal activity, and ectoenzyme profiles.
- Activities were compared to cloned gamma-interferon (IFN-gamma) and tested with anti-IFN-gamma antibodies.
Main Results:
- Two hybridomas, T-3 and T-9, exhibited distinct activity patterns.
- T-9 supernatant mimicked IFN-gamma activity, protecting resident macrophages from Naegleria lysates and exhibiting cytostatic effects.
- T-3 supernatant provided protection without IFN-gamma involvement, suggesting a different molecular moiety is responsible for this specific M phi activation.
Conclusions:
- Macrophage activation for pathogen destruction and tumor cell killing may involve distinct mechanisms and signaling pathways.
- T-cell hybridomas are valuable tools for dissecting complex lymphokine-mediated macrophage activation.
- A lymphokine distinct from IFN-gamma mediates protection against Naegleria lysate-induced cytopathic effects in macrophages.