Flow cytometry dot plots demonstrate coexpression of CD95 and CD28 (top) and CD25 and CD69 expression (bottom) on CD4⁺ T cells from a representative neonate (GB14, 7 days old). Like adults (data not shown), neonates have large numbers of memory (CD95⁺) and activated (CD25⁺CD69⁺) CD4⁺ T lymphocytes in the intestinal tract (jejunum, ileum, colon) compared with peripheral lymphoid tissues (spleen, lymph nodes, and blood). Central memory cells are defined by CD95 and CD28 coexpression (top, polygonal gates). Note that there are no effector memory cells (CD95⁺, CD28⁻) evident in any tissues. Plots were generated by gating on CD4⁺ lymphocytes.