Interaction between human polymorphonuclear leucocytes and Chlamydia trachomatis elementary bodies: electron microscopy and chemiluminescent response

Incubation of human polymorphonuclear leucocytes (HPMN) with highly purified Chlamydia trachomatis serotype L2/434/Bu elementary bodies (EB), in the presence and absence of specific antibody, resulted in a 10(3)-fold reduction of viable count after 24 h incubation. Electron microscopy observations indicated activation of the HPMN by the EB. Attachment of the EB to the HPMN cell membrane, formation of a cytoplasmic cup and EB-containing vacuoles were observed. In addition, two types of phagocytic vacuoles were observed after 30 min incubation; in one type, a single EB was tightly surrounded by the vacuolar membrane, while the other type was enlarged and held one or more intact EB or degenerated EB or both. A fuzzy coat was observed on EB located in the HPMN vacuoles only in the presence of specific antibody. Empty vacuoles containing degenerated EB were observed in the HPMN after 24 h incubation. HPMN exposed to EB of C. trachomatis produced a marked chemiluminescent response with a peak 14 times greater than the peak value of the control. A second stimulation with phorbol 12-myristate 13-acetate and zymosan was achieved. The chemiluminescent peak value in the presence of heat-treated EB (56 degrees C, 20 min) was 50% of that obtained in the presence of untreated EB. The significance of the chemiluminescent response in the killing mechanism of C. trachomatis EB by HPMN is discussed.