CD4 and infection: However, the fact that CD3+CD69+ cells are infected at greater rates than CD3+CD69neg T cells throughout infection (Fig. 5), combined with the fact that CD8+CD69+ cells increase and CD4+CD69+ T cells decrease in most tissues (Fig. 6) strongly suggest that CD69+CD4+ T cells are lost through direct infection and lysis, rather than “bystander” apoptosis or chronic immune activation of uninfected cells.