CD4 and HIV infectious disease: 11 Sánchez-Martínez Sánchez-Martínez A A Perdomo-Celis Perdomo-Celis F F Acevedo-Sáenz Acevedo-Sáenz L L Rugeles Rugeles MT MT Velilla Velilla PA PA Cytotoxic CD4+ T-cells during HIV infection Targets or weapons?