Smad4^{co/co;Foxn1Cre} mice display normal intrathymic T-cell development but have a reduced peripheral T-cell pool. (A) Thymus cellularity (i), absolute (ii), and relative (iii) TEC numbers of Smad4^co/co and Smad4^{co/co;Foxn1Cre} mice at different ages. (B) Relative numbers of different thymic subpopulations defined by CD44 and CD25 expression in the Lin⁻ thymocyte population to detail the DN1-DN4 developmental stages, and CD4, CD8, and CD3/TCR expression to assess DP and SP populations in neonatal (i), 6-week- (ii), and 16-week-old mice (iii). (C) Absolute (i) and relative (ii) numbers of splenic T cells at different ages. For all experiments, a minimum of 3 mice per group were analyzed. Values are mean plus SD. □ represents Smad4^co/co; ■, Smad4^{co/co;Foxn1Cre}. *P < .05, **P < .01, ***P < .005, ****P < .001.