HIV affects which of the following most commonly

Ref Robbins 9/e p246 The entry of HIV into cells requires the CD4 molecule, which acts as a high-affinity receptor for the virus (Fig. 4-27). This requirement explains the tropism of the virus for CD4+ T cells and its ability to infect other CD4+ cells, paicularly macrophages and DCs. However, binding to CD4 is not sufficient for infection; the HIV envelope gp120 must also bind to other cell surface molecules (coreceptors) to facilitate cell entry. Two cell surface chemokine receptors, CCR5 and CXCR4, serve this role. HIV envelope gp120 (noncovalently attached to transmembrane gp41) binds initially to CD4 molecules (Fig. 4-27). This binding leads to a conformational change that exposes a new recognition site on gp120 for the core- ceptors CXCR4 (mostly on T cells) or CCR5 (mostly on macrophages). The gp41 then undergoes a conformational change that allows it to inse into the target membrane, and this process facilitates fusion of the virus with the cell. After fusion, the virus core containing the HIV genome enters the cytoplasm of the cell.