Bone-marrow-derived

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...

(BMDM) refers to

cells that are generated in a research laboratory from mammalian

bone marrow Bone marrow is a semi-solid tissue found within the spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It is composed of hematopoietic ce ...

cells. BMDMs can differentiate into mature macrophages in the presence of

growth factor A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation. Usually it is a secreted protein or a steroid hormone. Growth factors are important for regu ...

s and other signaling molecules. Undifferentiated bone marrow cells are cultured in the presence of

macrophage colony-stimulating factor The colony stimulating factor 1 (CSF1), also known as macrophage colony-stimulating factor (M-CSF), is a secreted cytokine which causes hematopoietic stem cells to differentiate into macrophages or other related cell types. Eukaryotic cells also ...

(M-CSF; CSF-1). M-CSF is a

cytokine Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...

and growth factor that is responsible for the proliferation and commitment of

myeloid Myeloid tissue, in the bone marrow sense of the word '' myeloid'' ('' myelo-'' + ''-oid''), is tissue of bone marrow, of bone marrow cell lineage, or resembling bone marrow, and myelogenous tissue (''myelo-'' + '' -genous'') is any tissue of, ...

progenitor In genealogy, the progenitor (rarer: primogenitor; german: Stammvater or ''Ahnherr'') is the – sometimes legendary – founder of a family, line of descent, clan or tribe, noble house, or ethnic group.. Ebenda''Ahnherr:''"Stammvater eines G ...

s into

monocyte Monocytes are a type of leukocyte or white blood cell. They are the largest type of leukocyte in blood and can differentiate into macrophages and conventional dendritic cells. As a part of the vertebrate innate immune system monocytes also inf ...

s (which then mature into macrophages). Macrophages have a wide variety of functions in the body including

phagocytosis Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is ...

of foreign invaders and other cellular debris, releasing cytokines to trigger immune responses, and antigen presentation. BMDMs provide a large homogenous population of macrophages that play an increasingly important role in making macrophage-related research possible and financially feasible. __TOC__

Production

In order to produce BMDMs,

mesenchymal stem cell Mesenchymal stem cells (MSCs) also known as mesenchymal stromal cells or medicinal signaling cells are multipotent stromal cells that can differentiate into a variety of cell types, including osteoblasts (bone cells), chondrocytes (cartilage c ...

s are removed from the tibia or femur of mice. Since BMDMs are derived from bone marrow, withdrawn cells are healthy and naïve (or unactivated), regardless of the condition of donor mice. After removal, stem-cells are incubated with CSF-1. Without CSF-1, the cells enter an inactive state but can reinitiate growth and differentiation if stimulated later. Mature macrophages and fibroblasts, which may carry unwanted growth factors, are removed. Next, IL-3 and IL-1, two growth factors, are often added to increase yield and promote rapid terminal differentiation. Exogenous media containing growth factors and other serums must also be added to make the cells continually viable. Full growth and differentiation take approximately 5–8 days. Millions of BMDMs can be derived from one mouse and frozen for years. After being thawed BMDMs can respond to a variety of stimuli such as LPS,

IFN-γ Interferon gamma (IFN-γ) is a dimerized soluble cytokine that is the only member of the type II class of interferons. The existence of this interferon, which early in its history was known as immune interferon, was described by E. F. Wheelock ...

PAMPs Pathogen-associated molecular patterns (PAMPs) are small molecular motifs conserved within a class of microbes. They are recognized by toll-like receptors (TLRs) and other pattern recognition receptors (PRRs) in both plants and animals. A vast arra ...

NF-κB Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is a protein complex that controls transcription of DNA, cytokine production and cell survival. NF-κB is found in almost all animal cell types and is involved in cellular ...

, and

IRF3 Interferon regulatory factor 3, also known as IRF3, is an interferon regulatory factor. Function IRF3 is a member of the interferon regulatory transcription factor (IRF) family. IRF3 was originally discovered as a homolog of IRF1 and IRF2. ...

. These signals induce translation of genes that produce cytokines and determine if macrophages are M1 (pro-inflammatory) or M2 (anti-inflammatory). If BMDMs are not frozen, they age and become less viable as CSF-1 and growth factors in their media decreases. Proliferation of BMDMs can also be inhibited by a number of reagents. For example, growth and differentiation is dependent on CSF-1 and a functional CSF-1 receptor, a member of the

tyrosine kinase A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions. Tyrosine kinases belong to a larger cla ...

family. Without a functional CSF-1 receptors, stem cells cannot respond to CSF-1 stimuli and therefore cannot differentiate;

interferon Interferons (IFNs, ) are a group of signaling proteins made and released by host cells in response to the presence of several viruses. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten the ...

s can cause a down regulation of the CSF-1 receptor. Additionally, without stimuli like LPS to induce macrophage maturation to M1 or M2, mice accumulate a large pool of

s, the precursor cells to macrophages, which are less helpful for macrophage-specific research

References

{{Reflist Immunology