Quantitative and qualitative differences in IL-2 and IL-4 expression in primary and secondary T cell stimulation

Abstract

Lymphocytes were concanavalin A (Con A) primed and the signal was withdrawn 4–48 h post-stimulation by a-methyl-D-mannopyranoslde (αMM) treatment. Upon restimulation IL-2 and IL-4 RNA expression was found to be greatly enhanced. Re-expression of lymphokine RNA was dependent on signals delivered by Con A, antl-CD3 antibodies or phorbolester plus ionomycin, and could not be achieved by either IL-2, phorbolester or ionomycin alone. Increased IL-2 re-expression was only possible when αMM was added early after primary stimulation, while the ability for enhanced IL-4 RNA re-expression persisted. IL-2 and IL-4 RNA re-expresslon was characterized by Increases In steady state precursor RNA levels and thus, presumably, increased rates of transcription. However, the high accumulation of IL-2 RNA observed upon restimulation was also due to greatly increased RNA stability (>4 h versus 30 mln after primary stimulation). Thus, secondary expression of IL-4 RNA Is persistent and mostly due to quantitative changes in transcription, whereas enhanced re-expression of IL-2 RNA also results from altered post-transcriptional regulation. This phenotype, however, is only short lived.