CD48-Deficient Mice Have a Pronounced Defect in CD4+T Cell Activation

We have generated mice deficient in the expression of the lymphocyte cell surface antigen CD48 (Blast-1, BCM1, sgp-60) by gene targeting in embryonic stem cell. Mice homozygous for the CD48 mutation (CD48-/-mice) are severely impaired in CD4+T cell activation. Proliferative responses to mitogens, anti-CD3 mAb, and alloantigen are all reduced. Experiments in which T cells and antigen-presenting cells from either wild-type or CD48-/-mice were cocultured reveal that CD48 is important on both T cells and antigen-presenting cells. The most dramatic impairment was observed in experiments in which highly purified T cells were stimulated through the T cell receptor in the presence of the phorbol ester, phorbol 12-myristate 13-acetate. The results of these experiments raise the possibility that CD48 plays a role in signaling through the T cell receptor.