Biphasic increase in chemiluminescence of lymphokine-treated macrophages.

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Abstract
The effect of incubation time with lymphokines on macrophage activities was studied by use of the phorbol myristate acetate-induced luminol-dependent chemiluminescence method and cytotoxicity test. When thioglycollate-elicited ICR mouse peritoneal macrophages were incubated with lymphokines, their ability to generate chemiluminescence increased biphasically during incubation. That, is within one day, it reached a maximal level at about 4 h (early response), and then progressively decreased to the control level. However, when the incubation time was further prolonged, it began to increase again, and reached about 2-fold the control level after 3 d (late response). The increase in the chemiluminescence of lymphokine-treated macrophages with increasing incubation time is not due to the increase in the macrophage cell numbers. In contrast to the clear biphasic increase in chemiluminescence, there was no clear biphasic increase in cytotoxicity in lymphokine-treated macrophages. The activities in the lymphokine supernatants to induce the early and the late chemiluminescent response in macrophages disappeared together with the activity to induce cytotoxicity, on dialysis at pH 2 for 24 h or on heating at 80.degree. C for 30 min, but not at 56.degree. C for 30 min. Although the lymphokines increasing macrophage chemiluminescence were separated into two fractions in Sephadex G-100 gel filtration, each fraction had both activities to induce the early and the late chemiluminescent response, and the major fraction largely corresponded to that of the activity to induce cytotoxicity. These results suggested that there is a lymphokine which alters macrophage chemiluminescence biphasically by itself, and it may be interferon-.gamma.