MODULATION OF LYMPHOCYTE AND MONOCYTE ACTIVITY AFTER INTRAVENOUS IMMUNOGLOBULIN ADMINISTRATION IN-VIVO

In 12 patients with primary hypogammaglobulinaemia we investigated the in vivo effect of one bolus injection (400 mg/kg) of intravenous immu noglobulin (IVIG) on lymphocyte subsets and monocytes in peripheral bl ood, on plasma levels of soluble factors reflecting monocyte and lymph ocyte activity and on lymphocyte proliferation and generation of react ive oxygen species (ROS) from monocytes analysed in vitro. Several imm unological changes were induced by IVIG infusion. First, there was a s ignificant decrease in CD4(+)/CD8(+) lymphocyte ratio in peripheral bl ood, reflecting a significant increase in circulating numbers of CD8() lymphocytes. Second, although there was no significant change in pla sma levels of soluble CD8 antigen, there was a significant decrease in soluble CD8 antigen/CD8(+) lymphocyte ratio, suggesting a down-regula tion of CD8(+) lymphocyte activity, Third, there was a significant inc rease in plasma levels of neopterin, suggesting in vivo activation of monocytes/macrophages. Fourth, the was a down-modulation of mitogen-st imulated lymphocyte proliferation in vitro, and this down-regulation w as significantly correlated with the increase in plasma neopterin leve ls. Finally, there was a significant decrease in zymosan-stimulated, b ut not in phorbol myristate acetate-stimulated, ROS generation from mo nocytes as evaluated by nitroblue tetrazolium reduction. The ability o f IVIG administration in vivo to down-modulate lymphocyte proliferatio n and ROS generation from monocytes in patients with persistent immune activation may be relevant for the clinical effects of IVIG in a vari ety of immune-mediated disorders.