AGE-RELATED DEFECT OF PHOSPHOLIPASE-C ACTIVITY, DIFFERENTIAL EXPRESSION OF THE BETA(2) ISOFORM IN ACTIVE T-LYMPHOCYTES FROM AGED HUMANS

The activation of phosphoinositide-specific PLC is one of the early ce llular responses to various growth factors and mitogens. It is known t hat these functions are altered with ageing. Here we show that-the bet a(2) isozyme is decreased with ageing in a peculiar T lymphocyte subpo pulation involved in the immune response, namely the active T lymphocy tes. The presence and cellular distribution of PLC isozymes were inves tigated with immunochemical and immunocytochemical methods. The in sit u immunocytochemistry displayed the presence of the beta and gamma iso forms in the cytoplasm, while no reactivity for the delta isoform was observed regardless of the age. The immunoblot analysis showed an incr eased expression in the beta(2) isoform in the young and an equal expr ession of the gamma(1) isoform in either age group. Our findings sugge st that the age-related defect of PLC activity is possibly due to an i mpaired expression of isozymes in aged active T lymphocytes. (C) Ameri can Society for Histocompatibility and Immunogenetics, 1998. Published by Elsevier Science Inc.