Complement Component 8b (C8b)

Constituent of the membrane attack complex (MAC) that plays a key role in the innate and adaptive immune response by forming pores in the plasma membrane of target cells.Patients with deficiency of C8 suffer from recurrent neisserial infections, predominantly with meningococcus infection of rare serotypes. Most such patients are discovered among those having their first episode of meningitis at ages older than 10 years. C8 deficiency of the alpha and gamma subunits was found in 4 black families and no Caucasian families by Ross and Densen (1984), whereas C8B deficiency was reported in 12 Caucasian kindreds and no black kindreds. Wulffraat et al. (1994) described a family in which a 13-year-old boy was found to be homozygous for C8B deficiency and to have juvenile chronic arthritis of 6 months' duration.Antinuclear antibodies, anti-double-stranded DNA antibodies, and rheumatoid factor were not detected.