Expression and significance of leukocyte membrane cofactor protein transcript in systemic lupus erythematosus.

Membrane cofactor protein (MCP) is a complement regulatory protein ubiquitously expressed on most nucleated cells. Since MCP protects autologous cells from complement-mediated injury, it is suggested to have a protective role against the self-tissue damage in inflammatory conditions such as systemic lupus erythematosus (SLE). However, the relevance of MCP in human SLE is not well explored. To assess the significance of MCP in SLE, we studied expression of leukocyte MCP transcript in 60 healthy individuals (controls) and 60 patients with SLE and correlated that with the levels of circulating immune complex (CIC), C3, C3d and SLEDAI scores. The levels of leukocyte MCP transcript were significantly higher (p < 0.001) in patients with SLE than the controls. Furthermore, MCP transcript levels exhibited significant positive correlations with SLEDAI scores and CIC level and a negative correlation with C3d level in patients. Twelve patients were followed-up until remission. The levels of MCP transcripts decreased significantly during remission as compared with the state of active disease. These findings suggest that in SLE, the expression of leukocyte MCP at the mRNA level is closely related to disease activity. A protective role of MCP in response to increased disease burden may be speculated. The follow-up study suggested MCP as a potential disease marker.