Table 1.

Characteristics of cells of myeloid lineage in health and in the context of HIV infection.

Cell Type	Cellular Markers	Primary Locations	Average Life Span	Functions/Features	Interaction with HIV	References
Macrophages	CD68+ EMR1+ CD14	Mucosal surface Tissues Brain (Microglia) Lungs (Alveolar) Liver (Kupffer cells) Bone (Osteoclasts)	Week to Months	Phagocytose cellular debris and pathogens Antigen presentation Arginine production under stimulation M1/M2 polarization Tissue remodelling	Restricted HIV replication Resist cytopathic effects Neuropathogenesis Induce PD-1 expression Induce IL-10 production Major viral reservoir Activate CTL by cross-presentation of HIV antigens	[54, 56, 68, 71, 115]
Monocytes	CD14hiCD16-CD14+CD16+ CD14lo/CD16hi	Peripheral blood	Few days	Patrol blood for surveillance Precursor to macrophages Precursor to DCs Interact with LPS via CD14 Phagocytosis	Restricted HIV replication Resist cytopathic effects Neuropathogenesis Induce PD-1 Induce IL-10 CD16+ is more permissive Viral reservoir	[16, 50, 54, 56, 78]
Myeloid DCs	Lin−HLA-DR+ CD11c+ CD1c+ CD123−	Peripheral blood Cerebrospinal fluid	Week to Months	Antigen presentation Arginine production under stimulation Phagocytosis Induce T cells in cell-mediated immunity	Less productive viral replication Transfer in cis and trans Potential to use in vaccines Induce PD-1 Induce T cell IL-10 production	[81, 88, 91, 93, 128]
Neutrophils	CD15 CD16 CD62L CD33 CD13 CD11b CD11c CD24	Peripheral blood	Less than 2 days Or Several days when activated	Most abundant leukocytes Arrive first at an injury site Promote acute inflammation Modulate T-cell responses Regulate humoral response Induce M1/M2 macrophages Kill bacteria via NETs Produce antimicrobial peptides Phagocytosis	Infection not reported Binding through FC-g NETs inactivate HIV HIV induces DCs to produce IL-10 to counteract NETs. Production of a-defensins	[8, 105, 110]
Myeloid derived suppressor cells (MDSC)	HLA-DR- CD11b+ CD33+ CD14+ CD15- CD66b CD11b VEGFR1 CD62lo CD16lo	Peripheral blood	Few days	Prevent damage by acute and chronic inflammation. Impair T cell function via ROS, arginase-1 and cytokines Suppress IFN-g production Phagocytosis	Increase with plasma viral load Increase with CD4+ decrease HIV infection or exposure to HIV-encoded protein Tat could drive MDSC generation in vitro	[8, 120, 121]
Low density Granulocytes (LDGs)	CD15 CD33 CD13 CD11c CD24 CD16hi CD62Llo	Peripheral blood	Few days	Impair T cell function via ROS, arginase-1 and cytokines Induce PD-L1 on neutrophils Phagocytosis Decreased adhesion	Increase with plasma viral load Increase with CD4+ decrease Inhibit T-cell proliferation	[8, 111, 112]