Screening for complement deficiencies in patients surviving from epidemic meningococcal disease.

Sera from 132 patients surviving from meningococcal disease during the high-endemic period 1 January 1980 to 31 December 1984 on the Faroe Islands were screened for deficiencies of the complement (C) system by measuring hemolytic complement function in serum. Samples from 12 patients with reduced C function were further investigated by immunochemical quantification of individual C proteins. One patients was identified with C3-deficiency (C3-concentration 6% of normal) due to the presence of C3 nephritic factor (C3NeF) in serum. In addition, eight patients had minor aberrations in one or several complement proteins. It is concluded, that C deficiency is not an important risk factor during epidemics of meningococcal disease. The C3NeF activity could not be absorbed with Neisseria meningitidis group B, type 15, indicating absence of crossreactivity between neisserial antigens and C3NeF.