Table 1.

Major differences between monocytes, macrophages, phagocytes, and T-cells

Type of cells	Origin	Markers	Function/properties
Monocytes	Bone-marrow-derived cells of myeloid-lineage	Ly6Chi and Ly6Clow (in mice) CD14++/CD16± classical, CD14++/CD16+ intermediate, CD14+/CD16++ nonclassical (in human)	Circulate in blood (with a half-life of ~ 3 days)[157] and/or reside in subcapsular space of the spleen [136]; constitute ∼10% of peripheral leukocytes in humans and ∼4% in mice; differ from macrophages by lack of F4/80. CD11b, expression, and low expression levels of CD68 and MHC-II [158, 159]; capable to phagocytose, and have vessel patrolling function; circulating and spleen-residing monocytes have the same transcriptomic profile [136]; have the ability to be rapidly mobilized in large numbers to inflamed sites throughout the body; differentiate into macrophages and dendritic cells [160]
Macrophages	Yolk sac-derived erythro-myeloid precursors bypassing monocyte intermediate; hematopoietic cells of fetal liver, local hematopoietic foci in prenatal organism, from blood/spleen monocytes that penetrate tissues, and from local proliferation of tissue macrophages; seed tissues early in embryonic development and continue later prenatally and postnatally	Major populations - M1 (pro-inflammatory, classically activated): CD68+/CD206−, CD86+, iNOS, IL-6, TNF-α; M2 (anti-inflammatory, alternatively-activated): CD206+/CD163+, Arg1 [161, 162], differ in terms of transcriptomic and protein profiles related to given tissue/organ microenvironment, e.g., high expression of CD11a and EpCAM for lung macrophages, VCAM-1 and CD31 for spleen macrophages, CD93 and ICAM-2 for peritoneal macrophages [7–9, 163]	Mononuclear phagocytes capable to phagocytose various foreign microorganisms, particles, dead /apoptotic/senescent cells [164]; moreover having additional diverse functions: such as niche cells for erythropoiesis [165, 166], promoting/regulating of angiogenesis [167], lymphangiogenesis [168], vessel wall lumen regulation [169], wound healing, fibrosis, cell/organ involution during embryonic development (capillary regression in pupillary membrane) [170], surfactant excess removal in lung development [171], neuronal/synaptic pruning [172], osmotic/tissue volume/fluid sensing [106], insulin sensing in adipose tissue [173], norepinephrine metabolism [116], reverse cholesterol transport [174], iron recycling in spleen and liver [175]
cTM, cardiac tissue macrophages	As other macrophages; and from hemogenic endothelium of cardiac cushion tissue	As described in Table 2	As described in Table 2
Phagocytes	Bone marrow myeloid-lineage-derived precursors (granulocytes, monocytes, macrophages—professional phagocytes); epithelial cells, fibroblasts, dendritic cells—phagocytose with slower rate and less specifically—nonprofessional phagocytes [176]	Capable to recognize phagocytic receptors (“eat-me signals”)—phagocytosis is mediated by various pathways	Cells exhibiting phagocytic activity; phagocytosis is the uptake by the cell of relatively large particles (> 0.5 µm) into vacuoles, by mechanisms that are clathrin-independent and usually require actin polymerization. Particles involved are microorganisms (bacteria, viruses), dead cells, tissue remnants, tumor cells, senescent erythrocytes, ejected erythroblastic nuclei, spermatogonia in spermatogenesis, etc. [47, 177]
T-cells	Bone marrow hematopoietic common lymphocyte progenitor; differentiate in thymus gaining T cell receptor (TCR)	T-helper (CD4+), T-cytotoxic (CD8+), T-regulatory (T-reg; CD4+CD25+Foxp3+)	Seed various tissues, including cardiac; T-cells comprise about 3% of total cardiac leukocytes [178]. CD4 lymphocytes mediate inflammation and age-related cardiac dysfunction, as lack of these cells reduce inflammatory cytokine production [179]. Aged hearts have more CD8 than CD4 lymphocytes [179]. T-reg cells exhibit beneficial cardioprotective effect after myocardial infarction [180]