Complement activation by Coccidioides immitis: in vitro and clinical studies

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Abstract
Mycelial- or spherule-phase derivatives of C. immitis caused a decrease in vitro of total hemolytic complement [CH50] in serum from a non-sensitized person. Activation involved classic and alternative pathways as shown by depression of hemolytic C4 and by generation of products of activation of components C3, C4 and factor B. Functional C activity or immunoreactive levels of C components or both were measured in 23 patients with self-limited or disseminated coccidioidomycosis. Low CH50 was found in 9, usually during the early phase of primary illness, and was transient. Hemolytic C4 was low and the effect of inulin to decrease complement levels was blunted, suggesting that classic and alternative pathways may be deficient. Associated depression of immunoreactive levels of components assayed (C3, C4, C5, factor B and properdin) was not consistently found. This disparity raises the possibility of enhanced in vitro inactivation analogous to activation by immune complexes.