CD4 and Splenomegaly: This contributed to a moderate Fas-independent splenomegaly in the absence of Tlr9. While splenomegaly and lymphadenopathy are major features of the MRL.Faslpr strain, they are driven predominantly by the expansion of a TCRß+ B220+ CD4- CD8- "DN T cell" population not observed in Fas-sufficient MRL/+.