The immunobiology and immunopathology of chlamydial infections

Abstract

Chlamydiae are obligate intracellular bacterial pathogens of eukaryotic cells responsible for a wide variety of important human and animal infections. In humans, chlamydial infections are generally localised to superficial epithelial or mucosal surfaces, are frequently asymptomatic and may persist for long periods of time if untreated, inducing little protective immunity. Nevertheless, neutralising antibodies of limited efficacy are produced against the main chlamydial outer envelope protein, while gamma interferon (IFNγ) is chlamydiastatic and paradoxically may play a role both in chlamydial persistence and in protective immunity. Delayed hypersensitivity responses to chlamydiae caused by repeated or persistent infection are thought to be important in the development of the severe scarring sequelae characteristic of cicatricial trachoma and of chronic salpingitis. Chlamydial heat shock proteins bearing close homology with their human equivalents may be major targets for immunopathological responses and their expression is upregulated in IFNγ induced persistent infection. C. pneumoniae, a common cause of acute respiratory infection in humans, may persist in coronary arteries and is strongly implicated as a risk factor in atherosclerosis and in acute myocardial infarction. This paper reviews the immunology and immunopathology of chlamydial infections in the context of the unique biology of this fascinating but challenging group of organisms.

Characterization of Chlamydia pneumoniae Antigens Using Human T Cell Clones

“…T cell-mediated immunity is regarded as crucial for host defence against Chlamydia [7,19,20], and the final outcome of immunity to C. trachomatis seems to depend on the proteins that predominantly induce T cell activation [5,6]. Although only limited data exist on CMI reactivity to C. pneumoniae, our preliminary studies suggested that C. pneumoniae proteins have different roles as dominant activators of CMI responses in different subjects [14].…”

ChlamydiapneumoniaeInhibits Apoptosis in Human Peripheral Blood Mononuclear Cells Through Induction of IL-10

“…Chlamydia pneumoniae, the newest member of the chlamydial family, has been established as a common cause of acute and chronic respiratory disease worldwide and implicated in the pathogenesis of coronary artery disease (13,14). Monocytes/PBMCs have been postulated to serve as a vehicle for systemic dissemination of the infection (15,16).…”

“…The sporelike elementary bodies facilitate transit between cells. The metabolically active reticulate bodies are responsible for intracellular replication (13,14). During chlamydial intracellular growth, maintenance of the host cell's integrity is essential not only for supplying nutrients, but also for shielding the intracellular organisms from host phagocytosis.…”

Enhanced Inducible Costimulator Ligand (ICOS-L) Expression on Dendritic Cells in Interleukin-10 Deficiency and Its Impact on T-Cell Subsets in Respiratory Tract Infection

“…One study found that ICOS knockout (KO) mice had reduced Th17 cells (37), whereas other studies showed increased Th17 cells in the condition of ICOS or ICOS-L deficiency (36,38). Chlamydia, a genus of obligate intracellular bacteria, consists of human pathogenic species such as Chlamydia trachomatis and Chlamydophila pneumoniae, causing a diverse spectrum of human diseases involving ocular, genital and respiratory systems (39,40). No human vaccine is available to prevent chlamydial infections.…”