EFFECTS OF PHORBOL ESTERS ON LYMPHOCYTE STIMULATION

Summary

Principal Investigator: Andrea Mastro
Abstract: Primary lymphocytes are an excellent model for studying cell division. Unlike cell lines, lymphocytes remain in Go until stimulated. Mitogenic lectins along with macro-phages induce production of interleukin 1 (IL1), interleukin 2 (IL2), and their receptors which interact to cause proliferation. These interactions are not well understood. The tumor-promoter, 12-0-tetradecanaylphorbol-13-acetate (TPA) can immunomodulate lymphocyte proliferation in vitro. It can enhance or depress proliferation as well as differentiate lymphocytes with suppressor function. How it does this at the biochemical, molecular and cellular levels is not clear. While TPA alone is not mitogenic, its enhancing function seems due to synergism with compounds which contribute part of the proliferative signal. With mitogenic lectins such as Concanavalin A (ConA), TPA replaces accessory cells. Wheat germ agglutinnin (WGA) a non-mitogenic lectin is rendered mitogenic by TPA. TPA and calcium ionophores, by-pass the need for lectins. Finally TPA and IL2 are mitogenic. In contrast pretreatment of lymphocytes with TPA depresses their response to ConA and TPA, WGA and TPA, TPA and IL2. Moreover, pretreatment causes the induction of a subpopulation which bind peanut agglutinnin lectin (PNA) and can suppress the proliferative response of other lymphocytes. Except for the recognition of this PNA+ fraction the roles of subpopulations of lymphocytes under each condition are not known or is it known which are involved in stimulation, depression, and suppression of proliferation. Furthermore, it is not known how proliferation or lack of it reflects earlier events such as IL2 production and IL2 receptor expression. Finally, one can ask if TPA modulation of lymphocyte function in vitro is relevant for TPA's role as a tumor promoter in vivo. We plan to use primary cultures of bovine lymphocytes, reactivated blasts and an IL2 dependent line to compare these effects of TPA. Monoclonal antibodies and lectins will be used to screen for subpopulations. IL2 will be measured by bioassay. IL2 receptor will be measured by binding of radiolabeled IL2. Gene transcription for IL2 and IL receptor will be measured using cDNA probes. Finally, the immunomodulatory role of TPA in vivo will be followed during the course of skin initiation/promotion experiment. Lymphocytes from the spleens and lymph nodes of mice initiated with dimethylbenzanthracene and promoted with TPA will be examined for subpopulations using monoclonal antibodies for the major lymphoid populations. The cells will also be tested for suppressor activity.
Funding Period: 1978-09-01 - 1993-04-30
more information: NIH RePORT