AH50 AssayA screening test for defects in the alternative complement pathway, which shares late complement factors (C3 and C5-C9), but has unique early complement factors D, B, and P, and regulatory factors H and I. The alternative pathway is activated by bacterial polysaccharides and doesn’t require immune complex formation as does the haemolytic pathway (CH50). Patients with systemic bacterial infections in the presence of a normal CH50 may have an absent AH50 due to hereditary or acquired alternate pathway deficiencies. Patients with defects in the alternate pathway factors or late complement components are especially susceptible to recurrent neisserial meningitis.
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