Characterization of the ovine interleukin-2 receptor-alpha chain: differential induction on precultured alpha beta and gamma delta T cells.

A combination of concanavalin A (Con A)-stimulated ovine lymph node (LN) cells and Chinese hamster ovarian (CHO) cells stably transfected with the ovine interleukin-2 receptor-alpha (IL-2R alpha) chain cDNA (CHO IL-2R cells) were used in a differential immunization strategy to generate several monoclonal antibodies (mAb) against the ovine IL-2R alpha chain. The specificity of one of the mAb, designated mAb 9-14, for the ovine IL-2R alpha chain was demonstrated by its reactivity with Con A-stimulated LN cells and CHO IL-2R cells, immunoprecipitation of a 47,000 MW protein from CHO IL-2R cells and inhibition of IL-2-dependent proliferation of Con A-stimulated ovine LN cells. Examination of IL-2R alpha chain expression on resting lamb peripheral blood lymphocyte populations showed a high frequency of IL-2R alpha chain expression on CD4 T cells but not on CD8 T cells, CD45RA+ cells or gamma delta T cells, which comprise up to 60% of lamb peripheral blood T cells. The kinetics of IL-2R alpha chain induction on Con A-stimulated peripheral blood alpha beta and gamma delta T cells was compared. A rapid induction of IL-2R alpha chain expression on precultured gamma delta T cells but not alpha beta T cells was observed within 6 hr of Con A stimulation. A preculturing period was required to 'prime' gamma delta T cells for rapid responsiveness to Con A. Using appropriate inhibitors, we demonstrated that both transcription and translation events were required for rapid IL-2R expression on precultured gamma delta T cells and therefore the 'priming' of gamma delta T cells by in vitro culture did not involve an accumulation of IL-2R alpha chain mRNA or preformed receptors within these cells.