Natural killer and NKT cells in the male reproductive tract

•Infection and inflammation of the genital tract are thought to be the primary etiology of male infertility.•Natural killer (NK) and NKT cells play a pivotal role in the innate and adaptive immune responses.•NK and NKT cells maintain immune privilege and pathological antigens and cancerous cells in testis.•Indication of tumor recurrence (NK) and remodeling the immune microenvironment (NK T) in prostate cancer.•Proliferation of NK and NKT cells impair sperm quality and functions in semen.