Naive T cells from cord blood have the capacity to make Types 1 and 2 cytokines

We wanted to determine whether naive T cells could make the Types 1, 2 and 0 defining cytokines Interleukin (IL)-4 and Interferon (IFN)gamma. We show that stimulation of naive T cells (CD3(+)CD45RA(+)) derived from cord blood by phorbol ester (phorbol-12-myristate-13-acetate; PMA) plus Ionomycin ind uced detection of Types 1, 2 and 0 cells. Conversely, when we stimulated th e naive T cells through the T cell receptor (with anti-CD3 monoclonal antib ody alone) there was no detection of IFN gamma or IL-4 producing cells. Sti mulation with PMA and CD3 induced detection of only Type 2 cells. This unex pected finding shows that there is a high frequency of Type 2 cells within the naive T cell population, contrary to previously published reports. The highest percentage of Type 2 naive cells (10.5%) was obtained with 50 ng/ml PMA plus 50 mug/ml anti-CD3. Thus, we have shown that naive T cells derive d from cord blood have the capacity to make both Types 1 and 2 cytokines an d the frequency of cells producing these cytokines can be greater than 20%, depending on the stimulus used. (C) 2000 Elsevier Science B.V. All rights reserved.