CD4 and infection: In addition, a study on the relationship between AE infection and apoptosis of CD4+ T lymphocytes in infected mice has indicated that the expression of Bcl-2, C myc, TGF-β and apoptosis of CD+4 T cells can be significantly increased 25 weeks after infection [52], accordingly, the reduction in suppressor signals is probably due to the apoptosis of CD4+ T lymphocytes.