SERUM-SOLUBLE CD23 IN PATIENTS WITH HYPOGAMMAGLOBULINEMIA

Serum levels of the soluble form of the low-affinity receptor for IgE (FcERII, CD23) (sCD23) are elevated in autoimmune conditions associate d with hypergammaglobulinaemia and B cell hyperactivity. Very high lev els of sCD23 are found in patients with B-chronic lymphatic leukaemia (B-CLL) who are, however, frequently hypogammaglobulinaemic. We theref ore compared the serum levels of sCD23 in healthy controls (n = 33) wi th three conditions associated with hypogammaglobulinaemia (HGG) and v arying B cell numbers: X-linked agammaglobulinaemia (XLA, n = 12), com mon variable immunodeficiency (CVI, n = 20) and B-chronic lymphatic le ukaemia (n = 33). Serum levels of sCD23 showed a significant correlati on 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 compar isons 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 ce ll numbers. There was no overlap in sCD23 between patients with XLA an d this subgroup of CVI patients. Serum sCD23 is, therefore, derived pr edominantly from B cells, and is significantly related to the peripher al blood B cell count.