Soluble CD23 levels are elevated in the serum of patients with primary Sjögren's syndrome and systemic lupus erythematosus

Abstract

SUMMARY The low affinity IgE receptor FcɛRII (CD23) is important in several aspects of T and B cell function. In this study serum levels of soluble CD23 (sCD23) were measured in three groups: 26 female patients with systemic lupus erythematosus (SLE), 21 females with primary Sjögren's syndrome (pSS) and 25 normal healthy females. The concentration of sCD23 was determined using an enhanced chemiluminescent sandwich ELISA developed in this laboratory. Increased levels of sCD23 were observed in pSS and in SLE patients compared with controls (median 23·0 versus 8·6, P <0·0002 and 18·1 versus 8·6, P <0·002 respectively). While the median level of sCD23 was found to be higher in pSS than in SLE the difference was not statistically significant. Patients with SLE and pSS on glucocorticoid treatment had significantly lower levels of sCD23 than patients not on this treatment (median 28·9 versus 14·4, P <0·05). Amongst the control patients sCD23 was inexplicably lower in the female members relative to the males (median 8·5 versus 12·3, P <0·05). Although serum IgG and IgA levels were significantly elevated in pSS and SLE patients relative to controls there was no direct correlation between sCD23 and the serum levels of these immunoglobulins. We conclude that B cell hyperactivity which occurs in both pSS and SLE is associated with raised levels of sCD23.