RESPONSIVENESS OF ISOLATED T LYMPHOCYTES FROM MELANOMA PATIENTS AND NORMAL INDIVIDUALS TO STIMULATION WITH ANTI-CD3

Abstract

The immune system plays a very important role in controlling the growth of neoplasms as is evident by the fact that people with immune defects have a higher frequency of tumors. The purpose of this project was to perform a preliminary comparison of the response of T lymphocytes from cancer patients with that of lymphocytes from normal individuals after stimulation with anti-CD3. Peripheral blood T cells from eight melanoma patients and a control group of five normal individuals were evaluated for the ability to transduce a signal through the T cell receptor (TCR)/CD3 complex. The level of transduction was determined by measuring the increase in intracellular calcium ([Ca²⁺]₁) levels following activation with the monoclonal antibody anti-CD3 (OKT3). The concentration of free intracellular Ca²⁺ of unstimulated T cells from the patient samples was approximately 100 nM, similar to that of the normal individuals. Mean increases in [Ca²⁺]₁ after anti-CD3 stimulation in the melanoma patients were comparable to those of the normal controls. One patient had a value significantly lower than the normal range and one had a value significantly higher than both the other patients and the control group. In this limited study using unfractionated T cells and optimized stimulation conditions, no population differences were observed between the two subject groups. The surface expression of activation antigens on T lymphocytes from the patient and control groups before and after 24 hour anti-CD3 stimulation was also evaluated as an indication of T cell responsiveness. CD3 expression was downregulated on both CD4 and CD8 xii lymphocytes from normal donors and melanoma patients after stimulation with anti-CD3. The percentage of CD4+ and CD4- lymphocytes from both groups that coexpress CD25 increased after stimulation with anti-CD3, as did CD4+ and CD4- cells from both groups that coexpress CD69. After stimulation with anti-CD3 the percentage of CD4+ and CD4- cells that coexpress CD38 and HLADR did not significantly increase in either subject group. Variability in expression of all the activation markers existed between individuals, but no significant population differences were seen between the two subject groups. This prelimary study failed to distinguish differences in the response of T cells from melanoma patients and normal donors to anti-CD3 stimulation. The study was limited in scope, and the number of subjects in both study groups was restricted. No conclusions can be drawn from these studies regarding T cell defects in melanoma patients.