MATERNAL B-LYMPHOCYTES SPECIFIC FOR PATERNAL HISTOCOMPATIBILITY ANTIGENS ARE PARTIALLY DELETED DURING PREGNANCY

Although genetically different from its mother, a mammalian fetus bear ing paternal alloantigens is normally not rejected. To investigate one of the many possible mechanisms involved in this important biologic p henomenon, we analyzed the consequences of fetal alloantigen recogniti on on maternal B lymphocytes, We used transgenic mice expressing a uni que B cell receptor with a relatively high affinity for the MHC class I molecule H-2K(k) on most B lymphocytes, We provide the first evidenc e for an alloantigen-specific B cell deletion in the spleens and bone marrow of transgenic mothers bearing H-2K(k)-positive fetuses. This hi ghly reproducible deletion affects less than or equal to 80% of Id-bea ring B cells, starts at midpregnancy, and is only observed until term. Such a specific maternal B cell deletion could contribute to the succ ess of the fetal allograft.