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Back to Basics: Macrophages and Natural Killer Cells

Macrophages provide a first line of defense in the innate immune response to pathogens. They have the unique ability to engulf material (phagocytosis) and eliminate debris. In addition, they release biologically active proteins called cytokines and recruit other immune system cells to stop the infection from spreading. Macrophages have several different receptors on their surface that help them effectively identify and bind pathogens to promote phagocytosis and stimulate the release of cytokines.

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Ask A Biologist

Think of macrophages as cell-eating machines. Their name actually means “big eater” in Greek. Macrophages are the biggest type of white blood cells - about 21 micrometers - or 0.00083 inches. Still too small to see with your eyes, but big enough to do the important job of cleaning up unwanted viruses, bacteria, and parts of dead cells.

Function of Macrophages in Disease: Current Understanding on Molecular Mechanisms

Tissue-resident macrophages (TRMs) are heterogeneous populations originating either from monocytes or embryonic progenitors, and distribute in lymphoid and non-lymphoid tissues. TRMs play diverse roles in many physiological processes, including metabolic function, clearance of cellular debris, and tissue remodeling and defense. Macrophages can be polarized to different functional phenotypes depending on their origin and tissue microenvironment.

Macrophages

Macrophages perform critical roles in immune regulation during infectious disease, cancer, neurological disorders, and wound-healing, responding to a variety of cellular signals to change their response. Residing in every tissue of the body, macrophages take on tissue-specific forms, such as Kupffer cells and microglia, where they scavenge and engulf micro-organisms and apoptotic cells, a central role in host defense.

Macrophages as Double Agents

As immune cells macrophages fight infection. They also are a key driver in shaping the tumor microenvironment.

Macrophages in health and disease

Since their early description as mononuclear phagocytes in both invertebrate and vertebrate species, macrophages have become increasingly important for our understanding of human health and disease. Their fundamental attributes enable them to “clean” their surroundings by phagocytosing cellular material and regulating tissue repair and maintenance.

Macrophages: shapes and functions

Macrophages are cells of the innate immune system and represent an important component of the first-line defense against pathogens and tumor cells. Here, their diverse functions in inflammation and tumor defense are described, and the mechanisms, tools, and activation pathways and states applied are presented.

Macrophages: The 'defense' cells that help throughout the body

The term "macrophage" conjures images of a hungry white blood cell gobbling invading bacteria. However, macrophages do much more than that: Not only do they act as antimicrobial warriors, they also play critical roles in immune regulation and wound-healing. They can respond to a variety of cellular signals and change their physiology in response to local cues.

Macrophages: The Good, the Bad, and the Gluttony

It is evident that macrophages are essential for both homeostasis and disease pathology.

Macrophages: The Potent Immunoregulatory Innate Immune Cells

Monocytes/macrophages are one of the major innate immune cells involved in the process of recognition of pathogens and the cell debris originated as a result of apoptosis and their engulfment by the process of phagocytosis.

Origin Story: Finding on Macrophage Development Challenges Long-Held View

Macrophages are immune cells that exist in diverse forms in various tissues. They interact constantly with cancer cells and appear to both target them and assist them under different circumstances. A new finding sheds light on how macrophages develop into different types — a discovery that could alter some cancer treatment strategies.

The Cells That Eat, Regurgitate and Eat Your Tattoos Again

As a tattoo is given, macrophages descend to capture invading ink. Probably because the ink granules are too bulky for the microscopic Pac-Mans to break down, they hold onto the pigment, your body art shining through their bellies.

The role of macrophages in the resolution of inflammation

Macrophages are innate immune cells present in every tissue and necessary for homeostasis. Macrophages sense and respond to pathogens and other environmental challenges and participate in tissue repair after injury.

Tissue-specific macrophages: how they develop and choreograph tissue biology

There is mounting evidence of macrophages orchestrating fundamental physiological processes, such as blood vessel formation, adipogenesis, metabolism and central and peripheral neuronal function. In parallel, novel methodologies have led to the characterization of tissue-specific macrophages, with distinct subpopulations of these cells showing different developmental trajectories, transcriptional programmes and life cycles.

Tuning Macrophages for Immunotherapy

The term macrophage comes from the Greek words makros, meaning large, and phagein, meaning to eat. Macrophages patrol the body seeking any cell types that do not display the proper protein surface markers and consume these foreign intruders in a process called phagocytosis. This process is useful for removing a variety of foreign substances, including potentially cancerous cells. However, cancerous cells are able to exploit the body’s immune system to prevent destruction by macrophages and possibly encourage proliferation of the cancerous cells.

Understanding the Biology of Self-Renewing Macrophages

Macrophages have long been considered terminally differentiated immune cells that develop from monocytes and are unable to enter the cell cycle. Recent studies, however, challenge this view and propose that macrophages can indeed enter the cell cycle and self-renew.

What are Macrophages?

Macrophages are immune system cells that are vital to the development of non-specific defense mechanisms that provide the first line of defense against pathogens. These large immune cells are present in nearly all tissues and actively remove dead and damaged cells, bacteria, cancerous cells, and cellular debris from the body.

Resources

Professor David Hume FRSE FMedSci

David Hume is one of the world’s leading authorities in the field of macrophage biology. His research on macrophages spans nearly 30 years in which time he has covered just about every aspect of macrophages in health and disease.

BiteSized Immunology

Macrophages are specialised cells involved in the detection, phagocytosis and destruction of bacteria and other harmful organisms. In addition, they can also present antigens to T cells and initiate inflammation by releasing molecules (known as cytokines) that activate other cells.

Physiopedia

Macrophages are specialised cells involved in the detection, phagocytosis and destruction of bacteria and other harmful organisms.[1] They are a diverse phenotype of professional phagocytic cells derived from bone-marrow precursors and parent monocytes in the peripheral blood.