Macrophage Fcγ Receptors Expression Is Altered by Treatment with Dopaminergic Drugs

Macrophage Fcγ receptors have an important role in host defense and the pathophysiology of immune mediated disorders. Alteration of splenic macrophage Fcγ receptors expression predisposes to severe infection. Inhibition or blockade of splenic macrophage Fcγ receptors is one of the mechanisms by which immune cytopenias improve. Dopaminergic drugs have clinically significant regulatory functions on the immune response. Using an experimental model in the guinea pig we assessed the effect of commonly used dopaminergic drugs on the expression of macrophage Fcγ receptors. Three dopa-antagonists, bromocryptine, leuprolide, and pergolide, and seven dopa-antagonists, chlorpromazine, SCH 23390, metochlopramide, sulpiride, veralipride, alizapride, and cisapride, were studied. Following guinea pig treatment with dopaminergic drugs, the clearance of IgG-sensitized RBCsin vivo,thein vitrobinding of IgG-sensitized RBCs by isolated splenic macrophages and flow cytometry with monoclonal antibodies were performed. Treatment with dopa-agonists enhanced the clearance of IgG-sensitized RBCs, thein vitrobinding of IgG-sensitized RBCs by isolated splenic macrophages, and the cell surface expression of both macrophage Fcγ receptors, and vice versa, dopa-antagonists impaired macrophage Fcγ receptors expression. Macrophage FcγR1,2 was more sensitive than FcγR2 to such dopaminergic effect. These alterations of macrophage Fcγ receptors expression are mediated by both D1 and D2 dopamine receptors, with a major participation of D2 receptors. Dopaminergic drugs alter the clearance of IgG-coated cells by an effect at the expression of splenic macrophage Fcγ receptors.