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 lonomycin induced detection of Types 1, 2 and 0 cells. Conversely, when we stimulated the naive T cells through the T cell receptor (with anti-CD3 monoclonal antibody alone) there was no detection of IFNgamma or IL-4 producing cells. Stimulation with PMA and CD3 induced detection of only Type 2 cells. This unexpected 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 microg/ml anti-CD3. Thus, we have shown that naive T cells derived from cord blood have the capacity to make both Types 1 and 2 cytokines and the frequency of cells producing these cytokines can be greater than 20%, depending on the stimulus used.