Abstract C. trachomatis infections in women may cause pelvic inflammatory disease, chronic pelvic pain, and infertility. In the mouse model, genital Chlamydia disseminates systemically to infect the spleen. Removal of the spleen (splenectomy) abrogates hydrosalpinx pathology in the female reproductive tract (FRT), although it does not affect FRT Chlamydia clearance. Ascension of Chlamydia to the upper FRT (uteri, ovaries, oviducts) is critical for the development of hydrosalpinx. Over the course of genital infection, splenectomized mice exhibit significantly lower Chlamydia burden in the upper FRT and the GI tract compared to controls. Based on the report that Chlamydia-specific IgA secreted in the FRT protects against genital Chlamydia challenge, we hypothesized that splenectomy induces IgA secretion in the FRT. Examination of vaginal washes revealed that unlike controls, splenectomized mice exhibit Chlamydia-specific IgA by 4 weeks post-infection (wpi). However, the presence of IgA at this time did not explain the significant reduction in Chlamydia ascension observed by 2 wpi. Unlike controls, splenectomized mice additionally exhibit Chlamydia-specific IgM antibodies in vaginal secretions as early as 2 wpi. Naïve mice infected with Chlamydia pre-incubated with vaginal washes of splenectomized mice collected at 2 or 6 wpi exhibited reduced Chlamydia burden in the FRT, ILNs, spleen, and the GI tract at 3 and 7 days post-infection compared to controls. Secreted IgM and IgA thus neutralize Chlamydia, diminish its ascension in the upper FRT and thus abrogate the long-term hydrosalpinx pathology. This work reveals a previously unknown role that the spleen plays in the regulation of antibody secretion in the FRT mucosa. Supported by a grant from NIH (1 R21 AI159743-01)