Limited role of polymorphonuclear neutrophils in a pregnant mouse model ofsecondary infection by Chlamydophila abortus (Chlamydia psittaci serotype 1)

The aim of this work was to study the role of polymorphonuclear neutrophils (PMNs) in the clearance of infection, and in the development of specific i mmunity against Chlamydophila abortus (Chlamydia psittaci serotype 1) secon dary infection. A pregnant mouse model depleted of neutrophils by the RB6-8 C5 monoclonal antibody was used. No clinical signs were observed in deplete d or nondepleted mice after secondary infection and no significant differen ces were observed in the litter size between the infected and control group s. In PMN-depleted mice C. abortus was not detected in the materno-fetal un it but merely produced low, persistent levels of infection in spleen and li ver. In the non-depleted mice the level of infection was significantly lowe r, being resolved during the first few days post-reinfection. In both infec ted mice groups the immune response in the liver was quickly established an d was seen to be composed mainly of CD4(+) T lymphocytes and macrophages. A Th1 response characterized by the presence of IFN-gamma and TNF-alpha in s erum was observed during early infection, with significantly higher levels in the non-depleted animals. Our results suggest that PMNs have little infl uence on the control of C. abortus secondary infection, although they are a first line of defense and may influence the early production of TNF-alpha. and IFN-gamma. (C) 2000 Academic Press.