The effect of Chlamydia trachomatis on luminol-dependent chemiluminescence of human polymorphonuclear leukocytes: requirements for opsonization.

The factors involved in the in vitro interaction of two strains of Chlamydia trachomatis with polymorphonuclear leukocytes were studied by employing the technique of luminol-dependent chemiluminescence. Unopsonized, partially purified elementary bodies of chlamydia failed to induce a significant chemiluminescence response when compared with serum-activated zymosan (less than 90%). Opsonization of the chlamydia with human sera greatly enhanced the chemiluminescence response. This enhancement was independent of the presence or absence of antibody specific for chlamydia or of complement. Primate serum had 77% of the activity of human serum; nonprimate sera (sheep, cow, horse, and rabbit) demonstrated substantially less activity. The magnitude of the chemiluminescence response observed with opsonized chlamydia was also dependent on the chlamydia-to-polymorphonuclear leukocyte ratio, with the greatest effect seen at 10:1. Chlamydia opsonized with human sera containing less than 100 mg of IgG/dl did not stimulate chemiluminescence more than did unopsonized chlamydia. These results suggest that human IgG may interact with C. trachomatis independent of specific antibody-binding sites.