Reciprocal changes in complement activity and immune-complex levels during plasma infusion in a C2-deficient SLE patient.

Although systemic lupus erythematosus (SLE) is abnormally common in individuals with complement deficiency, conclusive evidence has been lacking for a direct causal relationship between disease manifestations and a missing complement component. A patient with C2 deficiency and SLE has been treated with 56 courses of fresh frozen plasma (FFP) infusions over a period of 8 years. Each infusion, involving a total of 12 units of FFP administered in equal doses over 4 consecutive days, has consistently resulted in a transient restoration of the classical pathway of complement, and a full clinical remission lasting 6-8 weeks. This report is concerned with changes in the levels of immune complexes, C2 and C3d during an infusion cycle. Four progressively rising peaks in C2 and C3d were observed during the 4 days of the plasma infusion, and these peaks coincided with four reciprocally descending troughs in the levels of immune complexes. Identical fluctuations have been consistent in all the plasma-infusion cycles that have so far been monitored, and their consistent association with clinical remissions indicates a causal relationship between the C2 restoration and clinical remissions in this C2-deficient SLE patient.