C3b receptor (CR1) expression on the polymorphonuclear leukocytes from patients with systemic lupus erythematosus.

Polymorphonuclear leukocytes (PMN) C3b receptor (CR1) numbers have been measured in 14 normal individuals and 15 patients with SLE. The results in the normals showed that PMN possess three distinct pools of CR1. CR1 expression was lowest at 0 degrees C (mean 86,000 +/- s.e.m. 7,000), but increased when the cells were incubated at 37 degrees C (125,000 +/- 16,000) or when the cells were exposed to the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP, 10(-5) mol 1) at 37 degrees C (207,000 +/- 21,000). The increased expression at 37 degrees C was not dependent upon protein synthesis, an intact cytoskeleton or energy. Although the response to FMLP did not require de novo protein synthesis, increased CR1 expression was dependent upon an intact cytoskeleton and energy. All three PMN CR1 pools were reduced in patients with active SLE, but were normal in those in whom the disease was inactive. Serial studies performed on three SLE patients showed that PMN CR1 numbers were low during periods of disease activity and increased during remission. These data suggest that low PMN CR1 numbers in SLE are a consequence of the disease.