Expression of Fcγ and complement receptors in monocytes of X-linked agammaglobulinaemia and common variable immunodeficiency patients

Abstract

Summary Recently we reported that monocyte phagocytosis and chemotaxis are impaired in X-linked agammaglobulinaemia (XLA) and common variable immunodeficiency (CVI) patients. Few data exist on the in vivo expression of receptors for the constant region of immunoglobulin (IgG) (FcγR) and complement receptors (CR) in these patients. The objective of this study was to investigate the expression of FcγR and CR on monocytes from XLA and CVI patients and compare it to that of healthy controls. Whole blood samples were obtained from 10 patients with XLA, 12 with CVI and 18 healthy controls. Monocyte phenotype was determined by flow cytometry with gating on CD14+ cells. Surface expression of FcγRI (CD64), FcγRII (CD32) and FcγRIII (CD16), CR1 (CD35) and CR3 (CD11b and CD18) was measured by determination of the proportion of CD14+ cells positive for each receptor and by receptor density. Compared to controls, a significantly higher percentage of CD16 and CD35+ monocytes from XLA (P = 0·002 and P = 0·007, respectively) were observed. The relative fluorescence intensity (RFI) expression of FcyRII (CD32) and FcyRIII (CD16) were significantly lower on CVI monocytes compared to controls (P = 0·001 and P = 0·035, respectively). XLA patients, who have a reduction of Bruton's tyrosine kinase (Btk), showed normal or increased percentages of monocytes expressing Fcy and complement receptors. CVI patients, who have normal expression of Btk, showed reduced expression of CD16 and CD32 on monocytes. Inefficient chemotaxis and phagocytosis, reported previously in XLA patients, could be due to defects of cytoplasmatic transduction mechanisms.