We characterized the sperm proteins recognized by the antibodies in mouse serum and epididymal fluid after immune tolerance disruption by performing mass spectrometry-based label-free quantitative proteomics. For this, we immunoprecipitated sperm cell protein extractions with serum and epididymal fluids from the proximal and distal epididymis of WT and Foxp3-DTR transgenic mice 2 weeks after Treg depletion.