FUNCTIONAL IL-2 RECEPTORS ARE EXPRESSED BY RAT LUNG TYPE-II EPITHELIAL-CELLS

Interferon (IFN)-gamma-induced inhibition of type II epithelial cell t hymidine incorporation (45% decrease vs. control) was restored by cocu ltures with mitogen-activated peripheral blood mononuclear cells (PBMC ) and conditioned media (CM) from mitogen-activated PBMC. Successive e xposure of type II cells to IFN-gamma and interleukin (IL)-2 produced similar alterations in thymidine incorporation. Given that IL-2 is a p owerful pleiotropic cytokine produced by lymphoid and myeloid cells, t he presence of IL-2 receptors (IL-2R) was assessed in primary cultures of rat type II pneumocytes (TIIP) and the nontransformed alveolar typ e II epithelial cell line L2. The presence of IL-2R membrane protein o n rat type II cells was established by immunodetection assays. The exp ression of all three murine IL-2R alpha-, beta-, and gamma-chain RNA t ranscripts in primary TIIP cultures and L2 cells was highlighted by re verse 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 ''p artner'' in the lung immune system. Consequently, it can be speculated that TIIP are new cellular targets for lymphokines using (IL-2R) gamm a-chain-bearing receptors in lung distal airspaces.