Chlamydophila abortus (Chlamydia psittaci serotype 1) clearance is associated with the early recruitment of neutrophils and CD8(+) T cells in a mousemodel

The immune mechanisms in response to Chlamydophila abortus (Chlamydia psitt aci serotype 1) infection were studied in C57BL/6 and CBA mice. The infecti on was monitored and the following aspects of the immune response were eval uated: the nature of the leucocyte infiltrate in the liver, the percentages of polymorphonuclear neutrophils (PMNs), macrophages and lymphocytes in th e spleen, and the concentrations of cytokines in serum. In addition, the se rum concentrations of IgG1 and IgG2a were determined. Both mouse strains sh owed a Th1-like immune response, with high concentrations of IFN-gamma and minimal levels of IL-4; however, C57 mice differed from CBA mice in showing milder clinical signs and earlier resolution of infection. The greater abi lity of C57 mice than CBA mice to eliminate chlamydophilae was related to t he establishment of an earlier innate immunity, based on a more pronounced PMN response, and on a greater presence of CD8(+) T cells. (C) 2000 Harcour t Publishers Ltd.