1. By: Fidelia Teodora Angelin Vania
Phagocytosis
By: Fidelia Teodora Angelin Vania

2. What is phagocytes?
Phagocytes are the white blood cells that protect the body by ingesting (phagocytosing) harmful foreign particles, bacteria, and dead or dying cells.
Phagocytosis: A mechanism by which single cells of the animal kingdom, such as smaller protozoa, engulf and carry particles into the cytoplasm.

3. HiStOrY
phagocytes were first discovered in 1882 by Ilya Ilyich Mechnikov, while he was studying starfish larvae. Mechnikov was awarded in 1908 (jointly with Paul Ehrlich) nobel prize in physiology or medicine for his work on phagocytes and phagocytosis.
in 1903, Amroth Wright discovered that phagocytosis was reinforced by specific antibodies which he called opsonins, from the greek opson, a dressing or relish.
phagocytes occur in many species; some amoebae behave like macrophage phagocytes, which suggests that phagocytes appeared early in the evolution of life.

4. Types of Phagocytes depending on how effective they are at phagocytosis:
The professional phagocytes include cells called neutrophils, monocytes, macrophages, dendritic cells, and mast cells.
Non-professional phagocytes, to emphasize that, in contrast to professional phagocytes, phagocytosis is not their principal function. Fibroblasts, for example, which can phagocytose collagen in the process of remolding scars will also make some attempt to ingest foreign particles
The main difference between professional and non- professional phagocytes is that the professional phagocytes have molecules called receptors on their surfaces that can detect harmful objects, such as bacteria, that are not normally found in the body

5. Non-professional Phagocytes Professional Phagocytes
Main location
Variety of phenotypes
Blood, lymph and lymph nodes
Lymphocytes
Skin
Epithelial cells
Connective tissue
Fibroblasts
Blood
Erythrocytes
Professional Phagocytes
Main location
Variety of phenotypes
Blood
neutrophils, monocytes
Bone marrow
macrophages, monocytes, sinusoidal cells, lining cells
Gut and intestinal Peyer's patches
macrophages
Skin
resident Langerhans cells, other dendritic cells, conventional macrophages, mast cells

6. PHAGOCYTOSIS IS THE PROCESS BY WHICH A MACROPHAGE TYPE WHITE BLOOD CELL ENGULFS A BACTERIUM IN A MEMBRANE- BOUND SHELL CALLED A PHAGOSOME. THE PHAGOSOME FUSES WITH A LYSOSOME WHICH CARRIES DIGESTIVE ENZYMES THAT DESTROY THE BACTERIUM. MACROPHAGES HAVE SPECIAL RECEPTORS THAT ENHANCE PHAGOCYTOSIS (PROFESSIONAL PHAGOCYTES)

7. fUnCtIoN
They are essential for fighting infections and for subsequent immunity.
Phagocytes are important throughout the animal kingdom and are highly developed in vertebrates.
one litre of human blood contains about six billion phagocytes.

8. Mechanism of phagocytosis

9. Mechanism of phagocytosis (cont.)
Phagocytosis in three steps (from the picture):
1. Unbound phagocyte surface receptors do not trigger phagocytosis.
2. Binding of receptors causes them to cluster.
3. Phagocytosis is triggered and the particle is taken-up by the phagocyte

10. METHODS 1. Oxygen-dependent intracellular
The killing of microbes is a critical function of phagocytes that is either performed within the phagocyte (intracellular killing) or outside of the phagocyte (extracellular killing).
For example, Intracellular:
1. Oxygen-dependent intracellular
When a phagocyte ingests bacteria (or any material), its oxygen consumption increases. The increase in oxygen consumption, called a respiratory burst, produces reactive oxygen-containing molecules that are anti-microbial.[ The oxygen compounds are toxic to both the invader and the cell itself, so they are kept in compartments inside the cell. This method of killing invading microbes by using the reactive oxygen-containing molecules is referred to as oxygen-dependent intracellular killing, of which there are two types.

11. 2. Oxygen-independent intracellular
Phagocytes can also kill microbes by oxygen-independent methods, but these are not as effective as the oxygen- dependent ones. There are four main types.
The first uses electrically charged proteins which damage the bacterium's membrane.
The second type uses lysozymes; these enzymes break down the bacterial cell wall.
The third type uses lactoferrins, which are present in neutrophil granules and remove essential iron from bacteria.
The fourth type uses proteases and hydrolytic enzymes; these enzymes are used to digest the proteins of destroyed bacteria

12. We will see an animation of phagocytosis
hill.com/sites/ /student_view0/chapter2/animat ion__phagocytosis.html

13. The story of the animation
In phagocytosis, phagoscytes are attracted to the area of invasion by chemical products of the microorganism, phospholipids released by injured mammalian cells.
The phagocytes moves into the area of invasion then attaches to the microorganism. The attachment is mediated by a variety of surface receptors including antibody, lipopolysaccharide and complement receptors.
For example, the C3b component of a bacteria or other particles and the binds to C3b receptors on the phagocytes. (the process of coating to enhance phagocytosis is called opzonization)

14. The microorganism is then engulfed by the phagocyte into a vacuole known as a phagosome. Vesicles in the cytoplasm is called lysosomes, fuse with the phagosome, releasing digestive enzyme such as lysozyme and proteases into phagosome. The structure resulting from this fusion is called a phagolysosome.
Inside the phagolysosome, microorganism are killed and digested. Finally the digested contents of the phagolysosome are eliminated from the phagocyte by exocytosis.

15. THANKYOU

16. DANKE 

17. Terimakasih 