Besides that, increased C1-INH complex concentrations were also found in previous publications investigating C1s/C1-INH complex levels as an indicator for classical pathway activation in RA and SLE patients (32) or (C1-INH)2 C1r-C1s complexes to indicate C1 activation in glomerulonephritis (31). Here, C1S is linked to systemic lupus erythematosus.