LOWERED EXPRESSION OF C3B RECEPTOR (CR-1) ON ERYTHROCYTES OF RHEUMATOID-ARTHRITIS PATIENTS

The number of C3b receptors (CR1) on erythrocytes (E) has been quantit ated by whole cell enzyme-linked immunosorbent assay (ELISA), using a monoclonal anti-CR1 antibody, in 46 healthy individuals as controls, 5 8 having rheumatoid arthritis (RA) and 3 hereditary angioedema patient s. The mean value of CR1 in RA (381/E) was significantly lower (p < 0. 001) when compared to normal controls (646/E). In hereditary angioedem a patients CR1 numbers (620/E) were found to be comparable to normal v alues. No significant difference was found between normal male (708/E) and female (598/E) subjects. Among the patient groups, those on stero id therapy (352/E) showed no change compared to others not receiving s uch therapy (408/E). The cumulative frequency curve of CR1 in the norm al population showed maximum inflection at 32% and 82%. This led us to conclude that there is a trimodal distribution of receptors in the co ntrol population. Such a contention is well supported by frequency his togram, when a small group interval (0-50) was chosen. However, if lar ge group intervals (0-100 or 0-150) were considered, a very close appr oximation to unimodal pattern was obtained. The factors actually contr ibuting to low receptor numbers are yet to be elucidated.