CD4 negative mice as a model for immunodeficiency.

CD4 is a co-receptor required for T cell helper functions. A mouse strain without CD4 expression has been generated. These animals, surprisingly have a normal CTL response and reduced, but not absent, humoral responses. A new population of MHC class II restricted CD4-CD8-TcR alpha beta+ T cells has emerged which possess helper function potential. These findings have important implications on disease situations where CD4 cells are decreased or absent.