Immunology of Non-Trachomatis Chlamydial Infection

halamydia are obligate intracellular parasites with co plexe reproductive cycle. The genus comprises four different species: C. trachomatis, C. pneumoniae, C. psittaci and C. pecorum. Most of the work concerning the immune response is found on C. trachomatis as it is a major public health problem throughout the world. However the other species are also of interest as C. psittaci is one of the most important zoonose in the world and C. pneumoniae, recently identified as a separate species, is a common cause of upper and lower respiratory infection worldwide. The seroprevalence of this agent is ranging between 40 and 70%. It has also been suggested that C. pneumoniae may play a role in asthma and in coronary disease. In contrast to C. trachomatis, C. pneumoniae and C. psittaci are able to infect different type of cells such as alveolar macrophages, human monocytes and endothelial cells. This explains the easy access to different organs of the host and the presence of chlamydia and their structural components into the circulation. These components can bind to antibodies present in the blood and form immune complexes which maintain inflammatory reactions in the vascular system. Infections in untreated man and animals with C. psittaci sometimes are very severe and may lead to death underlying the importance of the acute phase of these infections. One can notice that the exact physiopathology of this death is not fully understood. Is the endotoxin of C. psittaci far more aggressive than the one found in C. trachomatis? For those who recovered the questions of host resistance and immunity arise. As underlined by Storz to understand this problem of natural resistance and acquired immunity one has to consider the nature of these infectious agents as obligate intracellular parasites and their possibility to remain latent.