CELLULAR IMMUNOLOGY 70, 373-379 (1982) Effects of Prostaglandin E, and Preincubation on Lectin-Stimulated Proliferation of Human T Cell Subsets’ NORBERT GUALDE AND JAMES S. GOODWIN Department of Medicine. University of New Mexico School of Medicine, Albuquerque, New Mexico 87131 Received March 26. 1982; accepted April 19, 1982 Our laboratory as well as others has previously noted that sensitivity of lymphocytes to inhibition by prostaglandin (PG)E, is lost after overnight preincubation. We now show that the change in sensitivity to PGE2 with preincubation varies depending upon the T-cell subset in the culture. In phytohemaglutinin (PHA)-stimulated cultures of fresh cells, PGE2 inhibits proliferation of T cells as well as OKT4 (+) cells and OKT8(+) cells. In PHA-stimulated cultures of preincubated cells, PGEs slightly augments proliferation of T cells; however, PGE still inhibits OKT4(+) cells and causes marked augmentation of OKT8(+) cells. Thus the “loss in sensitivity” to PGEs with preincubation is actually a result of the balancing effect of PGE, inhibiting OKT4(+) cells and stimulating OKT8(+) cells. INTRODUCTION Prostaglandins of the E series (PGE) are hormones which modulate the immune response in vitro and in vivo (1). These products are mostly suppressors of lym- phocyte poliferative responses in vitro. The suppression by prostaglandins of the in vitro T-cell response has been linked to a so-called “short-lived” suppressor T- cell subset (2) and a soluble suppressor factor (1). Stobo et al. (3) has reported that different T-cell fractions, separated on density gradients, responded differently to PGEz stimulation in the presence of mitogens. The purpose of the present study was to establish the effects of PGEz upon phytohemagglutinin (PHA) or concanavalin A (ConA) stimulated T-cell subsets isolated by means of the OKT4 and OKT8 monoclonal antibodies which identify the helper/inducer and suppressor/cytotoxic human T cells, respectively. We also investigated the effect of preincubation of these T-cell subsets on their sensitivity to PGE;?. MATERIAL AND METHODS Isolation of peripheral blood T cells. Peripheral blood mononuclear cells (PBMC) were isolated from heparinized blood of healthy adult donors on Ficoll- Hypaque density gradients (4). Glass adherent cells were removed by incubation at 37°C for 45 min on glass petri dishes in RPM1 1640 with 20% fetal calf serum ’ Supported by a grant (AG 01245) From the U.S. Public Health Service and also from the Commission Interprofessionelle des Industries Laitieres (France). 373 0008-8749/82/100373-07$02.00/O Copyright 0 1982 by Academic PI-W, Inc. All rights of reproduction in any form reserved.