| Summary: | T cell activation is widely believed to depend on interleukin 1 (IL 1) provided by antigen (Ag)-presenting cells (APC). Because IL 1 is not a constitutive product of APC, we examined the features of its production during the interaction of murine T cell clones and APC. We observed that IL 1 was detectable in supernatants of most myoglobin-specific T cell clones grown in APC and Ag. Two of these T cell clones induced exceptionally high levels of IL 1 in their supernatants, and these same clones demonstrated the unusual restriction to I-E(k), which is a low responder type for sperm whale myoglobin. One of these clones was characterized additionally as to the mechanism of IL 1 induction. This clone rapidly stimulated IL 1 production in the APC population (detectable at 4 hr of co-culture) or in macrophages (MΦ) or a MΦ-like cell line. IL 1 induction was Ag dependent and H-2 restricted. Induction was radioresistant, both on the part of the T cell and of the IL 1 producer. The IL 1-induction process was attributable to a lymphokine produced by the T cell clone. This lymphokine was distinct form IFN-γ, TNF and CSF-1 and may account for a principal mechanism of T→APC signalling. The induced IL 1 was the same in size, co-mitogenicity, and pyrogenicity as lipopolysaccharide-induced IL 1.
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