Polyadenylic acid-polyuridylic acid (poly A : U) and experimental murine brucellosis. II. Macrophages as target cells of poly A : U in experimental brucellosis.

Results of and experiments suggest that the early suppression of brucella growth in double stranded polyadenylic-polyuridylic acid-(poly A:U-) treated mice was due to a non-specific activation of macrophages by poly A:U. Poly A:U administered intraperitoneally at the time of brucella infection failed to enhance T-cell mediated responses to the organism, namely delayed-type hyper-sensitivity to brucellin and adoptive transfer of immunity to the infection. Poly A:U did not augment the protective antibodies formed in response to infection. Although poly A:U has been previously found to suppress brucellosis in athymic (nude) mice, it did not enhance the thymus-dependent antibody response to sheep erythrocytes in brucella-infected nudes, suggesting that it did not significantly enhance maturation of their helper T-cell percursors. Increased macrophage spreading, an indication of activation, was seen immediately after administration of poly A:U and . Later on the infection spreading was suppressed, a phenomenon which appears to relate to the biphasic effect of poly A:U described in the accompanying paper. Peritoneal macrophages treated with poly A:U were stimulated to spread on plastic surfaces, even when T lymphocytes were removed with anti-Thy-1 serum and complement.