INDUCTION OF CD69 EXPRESSION IN T-LYMPHOCYTES BY REAGENTS TARGETED TO THE SUPPRESSION OF SPECIFIC CELLULAR ACTIVATION CASCADE COMPONENTS.
C.D. Morgan and M.P.Downs. Department of Pathology, Section of Immunology and Histocompatibility, Scott & White Memorial Hospital and Clinic, Temple, TX.

---

Surface antigen CD69 is regarded as the earliest detectable "activation" antigen since expression densities rapidly increase in lymphocytes within 2-4 hours of stimulation. These studies were conducted with the aims of reproducibly suppressing or inhibiting CD69 expression in T-lymphocytes in a non-lethal manner, and exploiting deficient cellular expression of this marker in the development of clinically-relevant assays relating to histocompatibility and immunotoxicology. To this end, the suppressive or inhibitory potentials of reagents targeted to specific components of the cellular activation cascade were evaluated by dual parameter flow cytometric analysis of CD69 expression responses in treated T-lymphocytes. The reagents were selected to: 1) block or inactivate membrane-associated kinases (TPKs) and intracellular signaling kinases (PKCs); 2) inhibit replicative processes by DNA strand intercalation; and 3) interfere with protein synthesis by suppressing normal transcription/translation mechanisms. Flow data revealed that genistein and herbimycin A (TPK inhibitors), staurosporin (PKC inhibitor), mitomycin C (DNA intercalator), and actinomycin D (inhibitor of protein synthesis) all unexpectedly induced significant CD69 expression in responding T-lymphocytes without secondary mitogenic stimulation. The kinetics of CD69 expression, the absolute numbers of responding CD69+ cells, and the resulting surface antigen densities were not uniform, however, suggesting altered surface phenotype responses to chemotherapy-induced stress. In conclusion, CD69 expression is modulated in T-lymphocytes by reagents considered 'inhibitory.'