Interleukin-12-dependent activation of human lymphocyte subsets.

Recently, we reported that IL-12 increased expression and function of CD26/DPPIV, this may be a new cellular pathway of the Th1-like immune responses. Here, we looked for a specific subset which would respond to CD26 upregulation by IL-12. Contrary to previously described results, under our culture conditions (1 microg/ml of PHA), IL-12 enhanced preferentially the CD8 cell proliferation. By using dual fluorescence analysis, IL-12-dependent CD26 expression was found in both CD4 and CD8 (previously CD26+ or CD26-) activated T cells and, moreover, the CD45RO percentage was unaffected. However, the density of CD45RO Ag (which was reported to coexpress with CD26) was impaired. These effects can be implicated in the biological functions of IL-12 and provide some clinical possibilities.