Functional IL-2 receptors are expressed by rat lung type II epithelial cells

Interferon (IFN)-gamma-induced inhibition of type II epithelial cell thymidine incorporation (45% decrease vs. control) was restored by cocultures with mitogen-activated peripheral blood mononuclear cells (PBMC) and conditioned media (CM) from mitogen-activated PBMC. Successive exposure of type II cells to IFN-gamma and interleukin (IL)-2 produced similar alterations in thymidine incorporation. Given that IL-2 is a powerful pleiotropic cytokine produced by lymphoid and myeloid cells, the presence of IL-2 receptors (IL-2R) was assessed in primary cultures of rat type II pneumocytes (TIIP) and the nontransformed alveolar type II epithelial cell line L2. The presence of IL-2R membrane protein on rat type II cells was established by immunodetection assays. The expression of all three murine IL-2R alpha-, beta-, and gamma-chain RNA transcripts in primary TIIP cultures and L2 cells was highlighted by reverse transcriptase-polymerase chain reaction analysis. Overall, these experiments demonstrate, for the first time, that type II epithelial cells can express functional IL-2R, confirming TIIP as a potential "partner" in the lung immune system. Consequently, it can be speculated that TIIP are new cellular targets for lymphokines using (IL-2R) gamma-chain-bearing receptors in lung distal air-spaces.