CD4 and AIDS: Given that the Tfh population is a subset of memory CD4 T cells, which have been shown to be highly prone to die by apoptosis and that the extent of apoptosis is predictive of further progression towards AIDS characterizing pathogenic lentiviral infections, depletion of splenic Tfh cells may be related to the occurrence of apoptosis [33,34,36,38,40,43,44,91–94].