SUPPRESSION OF MITOGEN-INDUCED IL-2R-ALPHA EXPRESSION IN PBL BY SERUMFROM MICROFILAREMIC RATS CHRONICALLY INFECTED WITH BRUGIA-PAHANGI

To study immunological responses in filarial infections, interleukin-2 receptor alpha (IL-2R alpha) expression in the peripheral blood lymph ocytes (PBL) of Lewis rats infected with Brugia pahangi was observed b y flow cytometry. During infection, no increase in IL-2R alpha was obs erved in either microfilaraemic or amicrofilaraemic rats. The PBL of r ats were stimulated with phytohaemagglutinin (PHA) and the frequency o f IL-2R alpha-positivity was examined. After microfilariae appeared, t he increase in the rate of IL-2R alpha-positivity in microfilaraemic r ats was less than in amicrofilaraemic rats. The anergy of IL-2R alpha expression in microfilaraemic rats was restored when their lymphocytes were cultured with normal rat serum. IL-2R alpha expression in normal uninfected rats decreased when cultured with serum from microfilaraem ic rats. These results suggest that microfilariae-related factors in r at serum suppress PHA-induced IL-2R alpha expression in PBL and thus i nhibit cell proliferation and host immunity.