CD4 and HIV infectious disease: Residual HIV replication in tissue compartments can be prominent because of low antiretroviral drug penetration (Estes et al., 2017; Fletcher et al., 2014; Lorenzo-Redondo et al., 2016; Rothenberger et al., 2019), and CD32 expression in CD4+ T cells is induced upon in vitro HIV infection (Abdel-Mohsen et al., 2018; Badia et al., 2018; Descours et al., 2017; Grau-Expósito et al., 2017).