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pubmed:abstractText |
Complement pathway activity in the killing of Pentatrichomonas hominis was investigated in this study. At 10(5) organisms per ml, P. hominis was completely killed by the presence of 1% normal human serum. In contrast, no killing effect on P. hominis was observed when specific antibodies were absorbed or when the complement was destroyed. Moreover, Mg2+-ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-treated serum had no killing effect on P. hominis, while serum heated at 50 degrees C or treated with zymosan killed P. hominis as well as did normal human serum. Further study using gel filtration (Sephacryl S-300) and affinity chromatography (protein A) revealed that immunoglobulin M (IgM; 20 micrograms/ml) alone was responsible for the complement activation in the killing of P. hominis, but both IgA (24 micrograms/ml) and IgG (180 micrograms/ml) had no effect on complement-mediated lysis. On the other hand, IgG at 1,260 micrograms/ml completely inhibited complement-mediated killing by IgM, suggesting that a blocking factor is present in IgG. The results of this study indicate that a mechanism of IgM-dependent classical complement pathway activation contributes to the killing effect of normal human serum on P. hominis.
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