CD4 and lymphopenia: In line with the overall diminished thymopoietic capacity of the transgenic thymus, the peripheral compartment exhibits T lymphopenia, albeit with normal ratios of CD4+ and CD8+ lymphocytes; as a result, the proportion of B cells (non-T cells) in the lymph nodes is increased (SI Appendix, Fig. S7), as B cell development in mice is not impaired by Foxn1 deficiency.