Immunological memory in B-cell-deficient mice conveys long-lasting protection against genital tract infection with Chlamydia trachomatis by rapid recruitment of T cells

The role of antibodies and antigen deposition Tor the development of immuno logical memory has been incompletely investigated. We addressed whether lon g-term protection and T-cell memory can be stimulated against a genital tra ct infection with human Chlamydia trachomatis serovar D in B-cell-deficient (mu MT) mice. At 6 months following a primary infection with C. trachomati s, both mu MT and wild-type (WT) mice exhibited strong and comparable prote ction against reinfection. Evidence of long-lasting CD4(+) T-cell memory wa s found in both mu MT and WT mice, typified by comparable delayed-type hype rsensitivity (DTH) reactions against chlamydial antigens. No bacterial or c hlamydial DNA was found in the genital tract of mu MT memory mice, suggesti ng that immunological memory was maintained in the absence of antigen. Wher eas few T cells were present in the genital tract of memory mice, rapid rec ruitment of CD4(+) and some CD8(+). T cells into the genital tract tissue w as observed after challenge with live bacteria. Accumulation of T cells in the genital tract was preceded by a short transient infection of similar ma gnitude in both mu MT and WT memory mice, arguing against a long-term prote ctive role of local antibodies. The rapid recruitment of CD4(+) T cells int o the genital tract was associated with a transient detection of interferon -gamma (IFN-gamma) mRNA in the genital tract in chlamydia-immune memory mic e, which was not round in naive. challenged mice. Thus, long-term protectio n in the genital tract against C. trachomatis infection is conveyed by IFN- gamma -producing CD4(+) memory T cells, which appear to be maintained in th e absence of antibodies and local antigen deposition.