Relationship of leukocyte CR1 transcript and protein with the pathophysiology and prognosis of systemic lupus erythematosus: A follow-up study

Complement Receptor 1 (CR1) is a key complement regulatory protein (CRP) involved in the clearance of immune complexes. Earlier, we reported a marked decline of leukocyte CR1 (L-CR1) transcript and protein in patients with active systemic lupus erythematosus (SLE) and suggested L-CR1 transcript as a putative non-invasive disease marker for SLE. This follow-up study involving 18 patients with active SLE was conducted for further confirmation of the relationship between L-CR1 and SLE. Blood samples from the patients were collected on day 1 of the diagnosis (0 month) and at different time intervals (3 and 6 months) for analysis of L-CR1 transcript and L-CR1 protein by semi-quantitative reverse-transcriptase-polymerase chain reaction (RT-PCR) and western blotting respectively. Within 6 months, 15 patients entered remission. On day 1, the mean values of L-CR1 transcript (8.42 ± 3.53) and L-CR1 protein (4683 ± 1094) in the SLE patients were 6 times and 12 times lower than the normal controls (n = 103). At the end of month 6, these values increased by 4.5 and 6.5 times respectively for CR1 transcript (37.86 ± 8.52) and protein (30,265 ± 8614). Simultaneously, the SLE Disease Activity Index (SLEDAI) scores decreased by 4.8 times (4.47 ± 3.32) as compared with the scores obtained on day 1 (21.45 ± 5.67). Moreover, CR1 values correlated negatively with the SLEDAI scores. Levels of L-CR1 protein and transcript remained low in the three patients who did not enter remission. All of the above results suggested that an increase in the levels of L-CR1 related to good prognosis. Since the levels of L-CR1 protein is influenced by variables like proteolytic cleavage and secretion from leukocytes, the values of L-CR1 transcript on day 1 and subsequent follow-up points may bring a better insight into the state of the disease activity. An extended follow-up study is needed to confirm the significance of L-CR1 as a prognostic marker for SLE.