To examine the impact of Ss infection on complement proteins and complement regulatory proteins in DM, we quantified the systemic levels of C1q, C2, C3, C4, C4b, C5, C5a, MBL (Lectin) complement proteins and complement regulatory proteins, Factor B, Factor D, Factor H and factor I in Ss+DM+ and Ss-DM+ individuals. The gene discussed is C4A; the disease is synovial sarcoma.