CD4 and infection: • Non-lytic mechanisms are more effective in controlling infection when the rate of CTL mediated killings is low relative to the rate of cell-mediated killings• Lytic mechanisms are more important when the rate of virus induced CD4+ T cell deaths is high relative to the rate of CTL mediated killing regardless of the number of CTLs• Lytic arm is more important to control infection• Non-lytic arm is more important to control virus replication• Presence of CTLs helps to reduce viral loads and maintain CD4+ T cell numbers