Bromelin for liquefaction of cervical mucus in sperm antibody testing: its effect on spermagglutinating immunoglobulin G.

Incubation of cervical mucus with the proteolytic enzyme bromelin is known to result in complete liquefaction of the gel. This effect has been used in the detection spermagglutinating antibodies in cervical mucus. However, the well-known papain-like effect of bromelin on human immunoglobulin G (IgG) might be expected to lead to an underestimation of the sperm antibody activity in cervical mucus. This possibility was investigated by studying the effect of bromelin on known amounts of purified IgG from four spermagglutinating sera. Serologic testing of bromelin-treated samples of cervical mucus mixed with purified IgG revealed no effect on spermagglutinin titers, whereas a significant effect was observed on purified IgG alone. Inert proteins in cervical mucus seem to protect the antibodies against degradation, apparently by substrate competition. Liquefaction of cervical mucus by bromelin seems to be a better basis for the assessment of the sperm antibody content of the mucus than extraction procedures, which have been shown to give a deficient yield.