Interleukin 7 (murine pre-B cell growth factor/lymphopoietin 1) stimulates thymocyte growth: regulation by transforming growth factor beta

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Abstract
The effects of interleukin 7 (IL 7) previously known as murine pre‐B cell growth factor/lymphopoietin 1 on the growth of murine thymocytes was investigated. In the presence of a suboptimal dose of phytohemagglutinin, IL 7 induced a dose‐dependent increase in thymocyte proliferation which was comparable to that induced by IL 1. Additionally IL 7 was shown to synergize with a suboptimal dose of IL 1 to enhance thymocyte proliferation. Thymocyte proliferation induced by IL 7, like that induced by IL 1, was inhibited when either recombinant transforming growth factor (TGF) β1 or β2 were added at the initiation of culture. Interestingly, IL 7‐driven thymocyte proliferation was considerably less susceptible to inhibition by TGF‐β1 or TGF‐β2 than that induced by IL 1. Taken together these results suggest IL 7 may activate distinct populations of thymocytes and/or act through a pathway distinct from that utilized by IL 1.