Question

Why is sperm not considered as an antigen even though it is foreign to the woman's body?

Answer 1

antigens and antibodies are found in bloood not in sperms

and moreover it, sperms are. male sex gametes for the formation of zygote and the female gamete needs that for fertillization

Answer 2

To tell in a simple sentence as because they don't come in contact with their blood,and it is the same reason why sperm itself foreign to the male's body doesn't get destroyed just because the blood testis barrier prevents entry of blood as a result keep them away from antibody mediated destruction.