However, recent reports described CD4+ cytotoxic T cells (CTL) in peripheral blood, i.e. ex vivo, in various human pathologies such as Human Immunodeficiency Virus (HIV) [22], Cytomegalovirus (CMV) [23], poxvirus [24], Influenza [25] and Epstein - Barr virus (EBV) infections [26], B-cell chronic lymphocytic leukemia [27] and rheumatoid arthritis [28]. Here, CD4 is linked to infection.