Deficiency of c7 with systemic lupus erythematosus. solubilization of immune complexes in complement‐deficient sera

Abstract

A woman with systemic lupus erythematosus (SLE) was found to have undetectable serum total complement (C) activity with marked reductions in levels of several C components. Recognition of rising C4, C3, and C5 levels coupled with sustained absence of hemolytic activity led to studies of individual C components that identified a persisting selective and complete absence of C7 hemolytic activity. Review of the literature indicated that the frequency of SLE is increased in patients with complete deficiency of a late-acting C component (7% as compared to 0.05% in the general population); however, the disease frequency is less than that observed in patients with complete deficiency of an early-acting C component (41% incidence in patients lacking C1, C4, or C2). In order to explore one possible basis for this association, the capacity of serum from the patient described herein and from patients with other C component deficiencies to mediate in vitro solubilization of immune complexes was studied by using a recently developed as-

Formation of soluble immune complexes by complement in sera of patients with various hypocomplementemic states. Difference between inhibition of immune precipitation and solubilization.

“…We obtained again fresh serum of patient 11 (mixed cryoglobulinemia IgMk-IgG) in which hemolytic C4 was 1% of normal, whereas other complement proteins were less depleted. The IIP assay was performed in the presence of absence of purified C4 (100 and 200% of hemolytic C4).…”

“…Assays have been devised to measure SOL and 1IP in vitro in sera of patients with various immune complex-mediated diseases (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Abnormalities have been found in different diseases, but no attempts have been made to compare these two functions in defined situations in order to determine their biological relevance.…”

Complement-Mediated Solubilization of Immune Complexes and Their Interaction with Complement C3 Receptors

“…Complement factors in the membrane at tack complex do not participate in CMS, as several investigators [8,52,81,94] have ob served normal CMS in sera lacking C5, C6, C7 or C8 ( fig. 2).…”

“…2). A pronounced reduction in the solubilization capacity of sera deficient in Clr and C2 was reported [94], but the solubil ization reaction was allowed to proceed for 30 min only. This is not sufficient time for CMS capacity measurements in cases where the initial reaction is retarded due to de creased classical pathway activity [8],…”

“…This has been demonstrated by testing sera defi cient in C5, C6, Cl or C8 [8,94]. Serum from a patient lacking factor I was tested in our laboratory and found to exhibit a CMS close to the negative control level.…”