PubMed · 643038
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M Kondo, H Kato, M Masuda. 1978-05-18. Levamisole and serum complement.. https://pubmed.ncbi.nlm.nih.gov/643038/
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Deficiencies of individual complement proteins may be accompanied by SLE or related syndromes. Deficiencies of the classic activation pathway are often involved. In cases of C4 and C2 deficiency, there is evidence that this association occurs more frequently than would be expected by chance. The clinical picture differs from classic SLE. There is an increased frequency of skin involvement, a decreased frequency of renal disease, low or absent levels of antibody to native DNA, and increased levels of anti-Ro (SS-A). The mechanism for the association probably involves the effects of C3 and C4 on the precipitation of immune complex solubility, or on their processing through cell surface c4b/c3b receptors on phagocytes. Disseminated or recurrent Neisseria infections are common in patients lacking the constituents of the terminal MAC that are important in killing these organisms.
To assess the role of superoxide dismutase in protecting Escherichia coli from killing by human serum and neutrophils, we constructed isogenic, smooth-lipopolysaccharide K-12 strains, either sod wild-type, delta sodA, or delta sodA delta sodB. The delta sodA delta sodB strain was killed by serum much more readily than either the wild-type or delta sodA strain. After allowing for this serum sensitivity difference, the delta sodA delta sodB strain also showed increased susceptibility to phagocytic killing by human neutrophils. These results indicate that superoxide dismutase protects E. coli from killing by serum (complement system) and by human neutrophils, possibly by a role in maintaining bacterial membrane structure.
We have sought to elucidate the responses of human peripheral blood neutrophils to antigenic surfaces complexed with human specific IgA antibodies obtained either as myeloma proteins that recognize staphylococcal alpha-toxin, or from the serum of patients with subacute bacterial endocarditis due to Streptococcus mutans, or from colostrum. In contrast to IgG, IgA antibodies bound to antigen-coated fluorescent microspheres, and subsequently exposed to complement (or not), did not promote phagocytosis, as measured by flow cytometric enumeration of cell-associated microspheres. Instead, IgA antibodies interfered with complement-dependent phagocytosis mediated by IgG antibodies. These properties were shown by different forms of IgA antibodies, including serum and secretory IgA, as well as by monoclonal or polyclonal antibodies. Neutrophils did not respond to the production of superoxide to IgA antibodies complexed with antigen-coated microspheres or with antigen deposited on a solid surface and IgA antibodies suppressed IgG antibody- and complement-mediated superoxide release. However, neutrophils pretreated with interleukin-8 ingested IgA-opsonized microspheres and released superoxide when exposed to IgA antibody-antigen complexes. IgG antibody-antigen complexes did not stimulate increased superoxide release in interleukin-8-treated neutrophils. These findings were consistent with a selective increase in the surface expression of Fc alpha R by interleukin-8-treated neutrophils. We conclude that IgA antibodies interfere with the phagocytic activities of normal circulating human neutrophils and may promote these activities in inflammatory neutrophils activated by interleukin-8 in which Fc alpha R is up-regulated.