Serum soluble CD23 in patients with hypogammaglobulinaemia

Abstract

SUMMARY: Serum levels of the soluble form of the low-affinity receptor for IgE (FcERII, CD23) (sCD23) are elevated in autoimmune conditions associated with hypergammaglobulinaemia and B cell hyperactivity. Very high levels of sCD23 are found in patients with B-chronic lymphatic leukaemia (B-CLL) who are, however, frequently hypogammaglobulinaemic. We therefore compared the serum levels of sCD23 in healthy controls (n= 33) with three conditions associated with hypogammaglobulinaemia (HGG) and varying B cell numbers: X-linked agammaglobulinaemia (XLA, n= 12), common variable immunodeficiency (CVI, n= 20) and B-chronic lymphatic leukaemia (n= 33). Serum levels of sCD23 showed a significant correlation with the CD19+ B cell count in both normals and patients with CVI (r= 0 65, P < 0·0001). Amongst the different clinical groups, serum levels of sCD23 were increased in the order XLA < CVI < normals < CLL (medians 2·5, 7·7, 11·1 and 540, respectively; P < 0·001 for all comparisons except CVI versus normals P < 0·03 in a one-tailed test). In the CVI group, serum sCD23 was lowest amongst four patients with low B cell numbers. There was no overlap in sCD23 between patients with XLA and this subgroup of CVI patients. Serum sCD23 is, therefore, derived predominantly from B cells, and is significantly related to the peripheral blood B cell count.