CD4 and systemic lupus erythematosus: Consistent with the proposed protective role of Treg cells in SLE 29, the proportion of FoxP3+CD4+ Treg cells and IL-10+CD4+Tr1 cells in the LNs of MRL/lpr, but not MRL/Mp, mice declined with age (although the absolute numbers increased), with kinetics that correlated with the initiation and progression of proteinuria.