The effects of calpain inhibition upon IL-2 and CD25 expression in human peripheral blood mononuclear cells

Calcium is an important contributor to T cell activation; it is also the ma jor factor in the activation of the calcium-activated neutral proteinase, c alpain. For this reason, we wanted to investigate if calpain has a role in T cell activation and what aspects of this activation calpain affects. As m easured by semi-quantitative reverse transcriptase-polymerase chain reactio n (RT-PCR), calpain inhibition decreased interleukin-2 (IL-2) and CD25 mRNA expression in a dose-dependent manner, at early time points following the initial activation, and over extended periods of time in activated human pe ripheral blood mononuclear cells (PBMCs). Using an enzyme-linked immuno-sor bent assay (ELISA) specific for human IL-2, we found that calpain inhibitio n decreased IL-2 secretion in a dose-dependent manner, shortly after activa tion, and continuously over time. Inhibiting calpain caused a dose-dependen t inhibition of CD25 cell surface expression and also inhibited expression shortly after activation and for at least 48 h. This study showed that calp ain has an integral role in the synthesis of the two important T cell activ ation factors, IL-2 and CD25. (C) 2001 Published by Elsevier Science BY.