Objectives:Expression of immunoglobulin (Ig) A Fc receptors (Fc&agr;R) and their saturation by endogenous lgA were studied on blood monocytes and neutrophils to evaluate the role of Fc&agr;R in the formation of increased serum levels of lgA and IgA‐immune complexes (IgA‐IC) observed during HIV‐1 infection.Methods:Peripheral blood samples were obtained from 45 patients at different stages of HIV‐1 infection and from 22 healthy volunteers. This study was performed using a quantitative flow cytometry method in which blood cells were stained with anti‐Fc&agr;R monoclonal antibodies (MAb) recognizing epitopes outside the IgA‐binding site and with F(ab')2fragments of anti‐IgA antibodies. Immunoprecipitations of radiolabelled surface Fc&agr;R molecules were analysed by sodium dodecylsulphate‐polyacrylamide gel electrophoresis under glycosylated and deglycosylated conditions.Results:This study reveals a diminished surface expression of Fc&agr;R on blood monocytes of HIV‐1‐infected patients, which follows disease progression. Fc&agr;R molecules on patients' neutrophils have a higher apparent molecular mass (60‐90kD) with normal protein core, suggesting expression of receptors with altered carbohydrate moieties. Increased levels of serum IgA significantly correlate with decreased levels of Fc&agr;R in HIV‐1‐infected patients. Surface Fc&agr;R molecules are saturated by endogenous IgA1 in both cell types.Conclusion:These findings suggest that defective expression and/or altered glycosylation of Fc&agr;R may result in receptor saturation, impairment of IgA catabolism and diminished clearance of IgA‐IC in HIV‐1‐infected patients. Fc&agr;R expression represents a new marker for disease progression.