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  • Last Updated : 05 Dec, 2022
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Phagocytosis is a process by which certain living cells called phagocytes ingest or immerse different cells or particles. The phagocyte might be a free-living one-celled organic entity, like a one-celled critter, or one of the body cells, like a WBC. In certain types of creature life, for example, one-celled critters and wipes, phagocytosis is a method for taking care of. In higher creatures, phagocytosis is essentially a protective response against contamination and intrusion of the body by unfamiliar substances (antigens).

In people, phagocytic cells safeguard the body by ingesting hurtful microorganisms like infections, microbes, and other tainted/kicking bucket cells. As a matter of fact, phagocytosis is an essential part of the insusceptible framework and is embraced by unique cells like neutrophils and macrophages. By annihilating the microorganisms, the safe framework stops the spread of contamination or microbes in the body.

Steps of Phagocytosis

Step 1: Phagocytic cell activation and chemotaxis

Chemotaxis is the mechanism by which phagocytes are drawn to and migrate toward a range of chemicals produced during the immune response during the first stage of phagocytosis.

Phagocytic cells in the human body are dendritic cells, polymorphic nuclear monocytes, eosinophils, basophils, and mononuclear phagocyte systems. Resting phagocytes are actuated by provocative middle people (bacterial items, cytokines, prostaglandins, and supplement proteins). Initiation builds their metabolic and microbicidal action. Initiated cells likewise express more glycoprotein receptors which assist them with arriving at the site of contaminations as well as to tie immovably with microorganisms. Neutrophils are quick to show up and are subsequently supplanted by macrophages.

Step 2: Identifying encroaching bacteria

The adhesion of the antigen to the cell membrane of the phagocytic cells is the subsequent stage of phagocytosis. Adherence causes membrane protrusions, known as pseudopodia, to spread out and consume the attached substance. Phagocytic cells have a variety of receptors that enable them to adhere to viruses or bacteria. Here are a few of these receptors:

  • Pathogen-associated chemical patterns are recognized by pattern recognition receptors (PRRs) (PAMPs). These include bacterial DNA, mannans, flagellin, pilin, teichoic acids, peptidoglycan, and lipopolysaccharides. For instance, following binding with PAMPs, scavenger receptors and toll-like receptors bind and internalize gram-positive and gram-negative bacteria.
  • Fc receptors: The Fc part of antibodies like IgG and IgM complexed with antigens can bind to Fc receptors (FcR) found on the surfaces of neutrophils and macrophages (bacterial cells or viruses). Opsonization is the term for the process that improves phagocytosis.
  • Receptors for complement (CR1): Phagocytic cells have complement receptors that bind to complement proteins that are combined with antigen-antibody complexes. For instance, macrophages that have C3b receptors bind cells or complexes that C3b has stuck to, which results in phagocytosis. MBLs (mannose-binding lectins) aid in promoting phagocytosis as well.

Stage 3: Ingestion and arrangement of phagosomes

Following attachment, actin filaments undergo polymerization and subsequently depolymerization, which causes pseudopods to emerge and engulf the bacterium. The material is contained within a phagosome, an endocytic vesicle, which is subsequently transported to the endocytic processing pathway, following the fusion of the pseudopodia.

Step 4: Phagolysosome formation

A phagosome travels along this pathway and eventually merges with a lysosome to produce a phagolysosome inside the cell.

Step 5: Formation of remnant bodies and microbial killing

Lysosomes have lysozyme as well as a number of cytotoxic and antibacterial compounds that can kill phagocytosed cells and germs. Either oxygen-dependent or oxygen-independent techniques are used to destroy microorganisms.

Reactive oxygen intermediates (ROIs) and reactive nitrogen intermediates, which have strong antibacterial activity, are produced in large quantities by activated phagocytes during oxygen-dependent killing. In phagocytic cells, a metabolic process known as respiratory burst activates membrane-bound oxidase, resulting in the production of superoxide anion, hydroxyl radicals, and hydrogen peroxide. Nitric oxide, hypochlorite, and other powerful antibacterial compounds are also produced inside the phagolysosome. Against bacteria, fungus, parasitic worms, and protozoa, all of these compounds had strong antibacterial action.

Oxygen Independent Killing: In addition to producing lysozyme, activated phagocytic cells also produce a number of hydrolytic enzymes (such as cathepsin G, elastase, collagenase, cathelicidins, and bactericidal permeability-inducing protein) that carry out their degradative functions without the need for oxygen. Additionally, active macrophages create a class of cytotoxic and antibacterial peptides known as defensins. Staphylococcus aureus, Streptococcus pneumonia, Escherichia coli, Pseudomonas aeruginosa, and Haemophilus influenza are just a few of the microorganisms that Defensins may eradicate. Tumor necrosis factor (TNF-), a cytokine with a number of functions and cytotoxicity for some tumor cells, is also secreted by activated macrophages.

Exocytosis or elimination in Step 6

Exocytosis is the process by which the phagolysosome’s digested contents are expelled.


Defective phagocytic process results in conditions such as.

  • Chediak higashi disease.
  • Chronic granulomatous disease.
  • Leukocyte adhesion deficiency.
  • Myeloperoxidase deficiency.

In Apoptosis

apoptosis, likewise called modified cell demise, in science, is a system that permits cells to fall to pieces when animated by the proper trigger. Apoptosis can be set off by gentle cell injury and by different elements inside or outside of the cell; the harmed cells are then discarded in a deliberate design. As a morphologically unmistakable type of customized cell demise, apoptosis is not the same as the other significant course of cell passing known as rot. Apoptosis includes a buildup of the core and cytoplasm, trailed by the cell dividing into obvious pieces for removal. In multicellular living beings, cell number regularly results from the pace of cell creation less the pace of apoptosis.

In Protista



A living being with eukaryotic cells is definitely not a creature, plant, or growth; they are assembled for accommodation however not all are firmly related.

Protista and Phagocytosis-A few single-celled protists, for example, amoebae, use phagocytosis to ingest food particles; it is in a real sense how they eat food. Since their whole body comprises one cell, they can ingest food particles by inundating them, and afterward digest these particles by interfacing with a lysosome.

Immune System

The immune system, a sophisticated set of defense mechanisms that are present in humans and other advanced vertebrates, aids in the rejection of disease-causing organisms (pathogens). In reality, nonspecific innate immunity and specific acquired immunity, two cooperative defensive systems, work together to confer immunity from disease. All germs are successfully repelled by nonspecific defense mechanisms, whereas specific immune reactions are targeted at specific invading kinds. Together, the two systems prevent germs from entering and multiplying inside the body. These immune systems also aid in the elimination of cancer-causing aberrant bodily cells.

Infectious agents will come into contact with cells that are responsible for removing foreign substances from the body if they are not successfully repelled by the chemical and physical barriers mentioned above. These cells are the innate immune system’s non-specific effector cells. They include natural killer cells, which target bodily cells that contain infectious organisms, and scavenger cells, a group of cells that directly combat infectious microorganisms. While some of these cells use various strategies to eliminate pathogenic pathogens, others engulf and kill them through the process of phagocytosis. These cells collaborate with elements of acquired immunity to fight infection, much like other innate immunity components do.

Phagocytosis is necessary for the body’s defense mechanism and plays important role in process of inflammation to contain the spread of infection and eliminate the dead & necrotized cells in the body.

FAQs on Phagocytosis

Question 1: What is a phagocyte?


Phagocytes, are the kind of cells that can ingest, and now and again digest, unfamiliar particles, like microorganisms, carbon, residue, or color. It immerses unfamiliar bodies by expanding its cytoplasm into pseudopods (cytoplasmic expansions like feet), encompassing the unfamiliar molecule and framing a vacuole. And expelling products by exocytosis.

Question 2: What are the functions of phagocytes?


Proficient phagocytes assume a focal part in natural resistance by wiping out pathogenic microorganisms, growths, and dangerous cells, and add to versatile invulnerability by introducing antigens to lymphocytes. Furthermore, phagocytes have an impact on tissue renovation and keep up with general homeostasis by discarding apoptotic cells, an undertaking shared by non-proficient phagocytes, frequently of epithelial beginning. 

Question 3: Which type of immune cell is the first to arrive at the site of an injury to start cleaning up?


Neutrophils within the first 24 hrs followed by other immune cells.

Question 4: Activity of phagocytosis occurs through which cells?


The phagocytes incorporate many sorts of white platelets (like neutrophils, monocytes, macrophages, pole cells, and dendritic cells). Neutrophils can discharge items that invigorate monocytes and macrophages. Neutrophil discharges increment phagocytosis and the development of receptive oxygen intensifies associated with the intracellular killing.  Consequently, the Activity of phagocytosis happens through Neutrophils and monocytes. 

Question 5: Which cell does not show phagocytic activity?


Phagocytes can phagocytose or kill unfamiliar cells and particles like microbes by ingesting them. Many platelets have this capability, including monocytes, neutrophils and macrophages. Basophils don’t have phagocytic movement. In this way, the right response is ‘Basophil.’

Question 6: What are Kupffer cells?


Kupffer cells are phagocytic cells seen in the liver, they help in removing bacteria from blood passing through the liver. It is a type of macrophage seen in the liver.

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