Implications for persistent chlamydial infections of phagocyte-microorganism interplay.

In vitro models of Chlamydia trachomatis inhibition by cytokines, human-monocyte derived macrophages (HMDM) and human polymorphonuclear leukocytes (HPMN) are discussed in an attempt to delineate the molecular basis of parasite-host cell interplay in persistent and chronic chlamydial infection. Interferon gamma (IFN) has been found to reversibly inhibit chlamydial growth at an early stage in the replicative cycle, while tumor necrosis factor (TNF) has a more profound effect on chlamydial growth resulting in production of aberrant reticulate bodies and enhancement of production of prostaglandin E2 (PGE2). Chlamydia trachomatis (serovar L2) replicate in HMDM while serovar K has been found to be restricted in these cells.

Leishmania major: inhibition of the chemiluminescent response of human polymorphonuclear leukocytes by promastigotes and their excreted factors.

The effect of various leishmanial preparations on the chemiluminescent response (CR) of human polymorphonuclear leukocytes (PMN) was studied. Almost no CR was observed with PMN stimulated with either Leishmania promastigotes or their excreted factors (EFs). Promastigotes added to PMN stimulated with phorbol myristate acetate (PMA), at a proportion of 20 to 1, respectively inhibited approximately 80-83% of the CR activity.

The persistence of Chlamydia trachomatis elementary body cell walls in human polymorphonuclear leucocytes and induction of a chemiluminescent response.

Human polymorphonuclear leucocytes (HPMN) were incubated with [35S]methionine-labelled Chlamydia trachomatis (serovar L2/434/Bu) elementary bodies (EB) and EB cell walls. No net loss in the TCA-precipitable radioactivity was observed over 24 h in the HPMN that had taken up EB cell walls. SDS-polyacrylamide gel electrophoresis of the labelled C.

Induction of DNA strand scissions in HeLa cells by human polymorphonuclear leucocytes activated by Chlamydia trachomatis elementary bodies.

Incubation of human polymorphonuclear leucocytes (HPMN) with Chlamydia trachomatis elementary bodies (EB) or phorbol 12-myristate 13-acetate (PMA) resulted in the production of superoxide anions (.O2-) and hydrogen peroxide (H2O2). Exposure of HeLa cells to EB- or PMA-activated HPMN and to EB alone, for 2 h, resulted in the formation of DNA strand scissions (nicks) in the HeLa cells.

Inhibitory effect of retinoic acid on the respiratory burst of adult and cord blood neutrophils and macrophages: potential implication to bronchopulmonary dysplasia.

Infants suffering from bronchopulmonary dysplasia (BPD) are known to have low levels of vitamin A, a factor which may be implicated in the pathogenesis of the condition. The ability of retinoic acid (RA) (one of the active forms of vitamin A) to influence the production of superoxide anion (02-) and hydrogen peroxide (H2O2) by stimulated human adult or cord blood neutrophils and macrophages has been studied. RA was found to inhibit the O2- and H2O2 production in a dose-dependent manner.

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.