Abstract: OBJECTIVE To evaluate the immuno-inflammatory toxicity of vaginal mucosa of acetic acid vaginal thermosensitive in situ gel(Acid-TISG) by using the optimized vaginal irritation model in the rabbits. METHODS Twenty-four rabbits were divided randomly into the blank gel group, Acid-TISG group (12.11 mg·mL^-1) and positive nonoxynol-9 (N-9) group (5.6 mg·mL^-1). Gel was administered through vagina to rabbits at 3 mL per day for 10 d. Cervicovaginal lavages (CVLs) were collected at pre-administration and 24 h after the last administration. The concentrations of interleukin-6 (IL-6) and tumor necrosis factor-α(TNF-α) in the CVLs were detected. The pathological examination of the vaginal tissues was conducted, and the vaginal irritation was assessed and scored. The expression of leukocyte common antigen-CD45RB and proliferating cell nuclear antigen (PCNA) in the vaginal mucosa was detected by the immuno-histochemistry (IHC) assay. RESULTS The vaginal mucosal epithelium in the rabbits of the Acid-TISG group was intact with no obvious inflammation infiltration, congestion and edema; while the exfoliation of mucosal epithelium cells and the increase of the inflammatory cells were obviously observed in N-9 gel group(P<0.05). There was no obvious positive expression of CD45RB cells both in the blank gel group and the Acid-TISG group, but the positive expression of CD45RB cells increased significantly in the N-9 gel group(P<0.05). The concentrations of IL-6 and TNF-α in CVLs, were significantly increased in the N-9 gel group(P<0.05) 24 h after administration while there were no significantly increase in both blank gel group and the Acid-TISG group compared with predose. CONCLUSION Acid-TISG is unlikely to cause vaginal mucosal irritation in the rabbits. The optimized rabbit vaginal irritation model can be used to evaluate the topical toxicity of the candidate vaginal drugs.