IDENTIFICATION AND CELLULAR-DISTRIBUTION OF THE RAT INTERLEUKIN-2 RECEPTOR-BETA CHAIN - INDUCTION OF THE IL-2R-ALPHA(-)BETA(-I RECOGNITION DURING T-CELL DEVELOPMENT IN-VIVO AND BY T-CELL RECEPTOR STIMULATION OF CD4(+)8(+) IMMATURE THYMOCYTES IN-VITRO() PHENOTYPE BY MAJOR HISTOCOMPATIBILITY COMPLEX CLASS)

A mouse monoclonal antibody (mAb) to the rat interleukin-2 receptor be ta (IL-2R beta) chain was generated using IL-2R beta cDNA-transfected mouse L929 cells for immunization and differential screening. This ant ibody, called L316, detects a cell surface protein with an apparent mo lecular mass of about 80 kDa. In peripheral lymphoid organs of young a dult rats, IL-2R beta expression is restricted to T and natural killer (NK) cells, and less than 10 % of IL-2R beta(+) cells co-express the IL-2R alpha chain. IL-2R beta was detected on all NKRP-1(hi) (NK-) and NKRP-1(lo) cells (T-lineage cells of unknown function), most peripher al gamma delta T cells and on 30-40 % of CD8 and 10 % of CD4 alpha bet a T cells. In the adult rat thymus, mAb L316 detects a small subset (a bout 1 %) of predominantly IL-2R alpha(-) cells which express cell sur face markers characteristic of mature T lymphocytes and contain a high proportion of CD4(-)8(-) and CD4(-)8(+) alpha beta T cell receptor (T CR)(+) thymocytes. TCR-V usage suggests that major histocompatibility complex (MHC) class I plays a more important role than MHC class II in the selection of these cells. On immature CD4(+)8(+) rat thymocytes, IL-2R beta cell surface expression is readily induced by TCR stimulati on ill vitro, supporting the idea that lit vivo, the IL-2R beta(+) phe notype is the result of TCR engagement during thymic selection.