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Patients with systemic sclerosis exhibited greater levels of COMP-C3b
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Serum levels of cartilage oligomeric matrix protein and the complement activation product C3b were elevated in patients with systemic sclerosis compared with controls in a recent study.
Researchers analyzed serum and skin punch biopsies from 80 patients with confirmed systemic sclerosis (SSc) for the presence of cartilage oligomeric matrix protein (COMP) and COMP-C3b complexes. Depending on the level of skin involvement, patient disease was classified as limited cutaneous SSc (lcSSc; n=40) or diffuse cutaneous SSc (dcSSc; n=40). All SSc patients had samples collected again 3 to 5 years later to assess changes in COMP-C3b complexes. Researchers also obtained samples from 97 healthy controls at baseline.
Compared with controls, COMP and COMP-C3b serum levels were elevated in SSc patients (P<.0001). Across lcSSc and dcSSc patients, COMP-C3b levels were similar, although dcSSc patients had higher serum concentrations of COMP than lcSSc patients (P<.0001). COMP-C3b levels decreased in both groups at the second assessment, but was only significant among patients who were exposed to immunosuppressants (P=.007 for dcSSc; P=.0002 for lsSSc), excluding prednisolone.
When analyzing biopsies via COMP-staining from seven dcSSc patients and three controls, researchers found no statistically significant colocalization between COMP and C3b. Just two patients showed about 30% of stain overlapping, which indicated that COMP-C3b complexes formed after COMP was distributed into the circulation.
“COMP-C3b complexes are found in the serum of patients … with dcSSc and lcSSc although their levels relate more to individual inflammatory parameters in dcSSc,” the researchers concluded. “These complexes seem to form when COMP is released from the skin into the circulation, and therefore it seems that COMP itself does not drive complement activation and deposition in the skin in SSc.”
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