CD8A and cartilage disease: To more definitively determine if mature, conventional CD4+ and CD8+ T cells, which are the usual intended target of CD4-Cre transgenesis, were responsible for cartilage disease and nodule formation in Sos1/2 dKO mice, we crossed Sos1/2 dKO mice to mice deficient in RAG2, a recombinase that is required for the formation of mature T and B lymphocytes.