Bar charts demonstrating percentages of total CD4⁺ T cells and memory (CD95⁺) CD4⁺ T cells in various tissues of SIV-infected and uninfected age-matched normal neonates at various stages of acute infection or age. Note that when examining the changes in total CD4⁺ T cells (A) there is marked depletion of CD4⁺ T cells in the intestine (jejunum, ileum, and colon) by 14 days of SIV infection, but minimal changes in CD4⁺ T cells occur in the blood, lymph nodes, or spleen (A). The selective loss of intestinal CD4⁺ T cells is a direct reflection of the percentage of memory cells in these tissues before infection (B). Note that intestinal tissues have much higher percentages of memory CD4⁺ T cells before infection and that these are selectively eliminated in acute SIV infection (B). Data represent percentages of CD4⁺ cells gated through CD3⁺ T cells (A) or CD4⁺CD95⁺ T cells gated through lymphocytes (B) from groups (standard error bars) or individual animals as described in Table 1. SIV-infected (▪) and uninfected (□) age-matched normal neonates.