During hematopoiesis, myeloid cells develop from a common myeloid progenitor (CMP) found in the bone marrow. This lineage—which includes monocytes, granulocytes, erythrocytes, and platelets—is a primary component of the innate immune system and serves as a first line of defense against infection.
Related: Immunology: What are lymphoid cells and how are they identified?
This blog explores the main types of myeloid cells as well as key markers used to identify them.
Researchers have identified a number of distinct subtypes of myeloid cells, many of which can be further subcategorized into different functional states, and each playing a unique role in the immune response. The ability to accurately identify and quantify these subtypes is essential for understanding which cell populations are recruited and activated in response to certain pathogens and how they contribute to the resolution of immune challenges.
A few different methods can be used to distinguish myeloid lineage cell types. At a basic level, myeloid cell subsets can be identified based on their morphology and distribution within tissues or blood. However, full classification typically requires immunophenotyping, a technique that leverages antibodies to detect the expression of distinct cell surface molecules, which can be performed using assays such as flow cytometry or immunohistochemistry (IHC).
Immunophenotyping generally involves using panels of antibodies that recognize specific cluster of differentiation (CD) markers—cell surface molecules expressed by different cell types at various stages of differentiation. By analyzing CD marker expression patterns, researchers can detect and quantify the presence of specific immune cells within a mixed population.
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CMPs develop into a stunning array of terminally differentiated myeloid cell types. Major branches within this lineage include:
Megakaryocytes, which produce the platelets necessary for normal blood clotting.
Erythrocytes, or red blood cells, which are responsible for carrying oxygen to tissues.
Granulocytes, which include basophils, eosinophils, mast cells, and neutrophils.
Monocytes, which serve as progenitors for macrophages and dendritic cells.
Each type of myeloid cell participates in the immune response in a distinct way. For example, basophils contribute to many inflammatory reactions and release heparin, an anticoagulant that slows blood clot formation. Eosinophils are known for their role in defending against parasitic and viral infections, primarily through the release of major basic proteins and ribonucleases. Neutrophils, the most abundant type of granulocyte, act as first responders at sites of inflammation and infection, where they attack and remove invading microorganisms through phagocytosis, degranulation, and formation of neutrophil extracellular traps, or NETs.
When tissues are injured or infected by a pathogen, monocytes in the blood are recruited to the affected tissue, where they may differentiate into macrophages. After differentiation, macrophages detect foreign antigens and damaged cells and destroy them via phagocytosis. Upon completion of this process, macrophages can also process and present antigens to T cells, leading to their activation.
Dendritic cells also use phagocytosis to engulf cellular and foreign material, which they process and present as antigens to T cells. While other types of immune cells can present antigens to T cells, dendritic cells, along with macrophages and B cells, execute this function far more frequently and are known as professional antigen-presenting cells (APCs). APCs serve as critical links to relay information about pathogens between the innate and adaptive immune systems.
Accurately identifying myeloid cell subsets relies on the use of well-characterized phenotyping markers. While the expression of some markers is restricted to specific immune cell lineages, allowing for phenotyping with a single readout, analysis of multiple markers is generally required to determine the phenotype and maturation state of myeloid cells due to overlapping expression patterns.
For example, CD11b can be used as a broad, pan-myeloid marker, but additional readouts are needed to identify subsets and functional states.
IHC analysis of paraffin-embedded mouse spleen using recombinant monoclonal antibody CD11b/ITGAM (E4K8C) Rabbit mAb #93169.
Immune Cell Marker Pathway Guides
Need a quick reference guide for immune cell markers? Download our comprehensive immune cell marker pathway guides to explore human and mouse markers, as well as relevant CST antibody products validated for IHC and flow cytometry.
Updated May 2025. Originally published May 2020. CST Content Marketing Manager Alexandra Foley, and Tamar Tamar Aprahamian, PhD, founder of JetPub Scientific Communications, contributed to this blog.25-ICT-56550