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Immunology of HIV-1 infection

Jenna A Rychert, PhD
Eric S Rosenberg, MD
Section Editor
John G Bartlett, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Innate and adaptive immune responses play a role in controlling HIV replication. Yet, immune dysfunction is common in HIV-infected individuals and the virus has developed multiple strategies to evade host defenses. Thus, in most untreated individuals, viral replication is not fully contained, resulting in persistent viremia, progressive disease, and the development of acquired immunodeficiency syndrome (AIDS).

This topic is an introduction to the immunology of HIV infection and begins with a glossary of some of the common terminology used in the field. Other factors governing the progression of HIV infection are discussed elsewhere. (See "Factors affecting HIV progression".)


Viral entry — Infection begins when the envelope glycoprotein (gp120) of HIV binds to its cellular receptor, CD4. After a conformational shift, gp120 then binds to a coreceptor, either CCR5 or CXCR4 [1,2].

CCR5 and CXCR4 — CCR5 and CXCR4 are chemokine receptors that are expressed on T cells, macrophages, and dendritic cells. These molecules normally act as receptors for chemokines, proinflammatory chemicals that are released in the setting of inflammation. CCR5 and CXCR4 are expressed on different cell types; thus, the tropism of a viral variant is partially determined by its coreceptor preference.

R5 viruses — R5 viruses utilize CCR5 as a co-receptor. Phenotypically, these viruses are macrophage-tropic and are sometimes referred to as "M-tropic viruses".


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