CD4 and autoimmune uveitis: When the frequency of the P2.U2 transgenic T cells was reduced in the mixed bone chimeric mouse experiments, autoimmune attack on the retina still occurred in 3/9 AireGW/+ recipients and was not seen in any out of 17 Aire+ recipients, again emphasizing a key role for Aire in preventing autoimmune uveitis in the context of an additional challenge to immune tolerance, in this case, an increased frequency of autoreactive CD4 T cells.