Phygocytosis.pptx . . . . . . . . . . . . . . . . .

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1. Phygocytosis Miss Maria Sajjad

2. Phygocytosis Derived from a Greek word “ Phagein ” to devour, eat hungrily Kytos means cell Osis means process Defination Process of engulfment and destruction of solid particles such as bacteria,dead tissue and foreign particles .

3. The process by which a phagocyte (a type of white blood cell) surrounds and destroys foreign substances (such as bacteria) and removes dead cells . Principle The bacteria are recognized by surface receptors on a phagocyte .  The phagocyte engulfs the bacteria and a phagosome is formed . Phagosome formation requires many antimicrobial factors during maturation.

4. Important function of neutrophil and macrophages WBC engulf and destroy foreign particles Wbc phygocytes only harmful and foreign substances.

5. Phygocytes The cells performing phygocytosis are called phygocytes . The cells types are Neutrophils Monocytes Macrophages In blood its monocytes when entre in tissue changes to macrophages

6. Selection for phygocytosis occurs because Rough surface of foreign particles No protective protein coat opsonization

7. Steps Recognition Recognition of microbes through receptors Phygocytic cells have receptors with the help of these receptors recognize microbes

8. Receptors are Mannose receptors Scavangers etc Leukocytes have Mannose binding receptors Microbes have mannose sugar Receptors recognize mannose sugar

9. Scavangers Low density lipoprotein on microbes surface Neutrophil recognize LDL Efficacy of microbes increase if microbes have OPSONIN add through Opsonization If opsonin on microbes is present ,make it delicious,phygocyte cells eat rapidly

10. Opsonins IgGAb C omplement system protein C3b Plasma lactin Opsonization refers to the process of coating of bacteria by the opsonins Bacteria have opsonin coated Phygocytes have opsonin receptors The opsonin coated bacteria gets attached to the surface of phygocyte through the opsonin receptors.

11. Engulfment Neutrophil make cytoplasmic projection surrounded microbes Formation of cytoplasmic pseudopods by the phygocytes around the bacteria. Bacteria is endocytosed and is contained in a vesicle thus forming phygosomes The phagosomes fuses with nearby lysosomes to form phygolysosomes

12. Lysosomes discharge all their digestive agents bactericidal into vesicle( hydrolytic enzymes)

13. Killing Methods

14. Oxygen dependent Reactive oxygen species ROS capable of causing damage to biomolecules like protein ,lipid , nucleic acid. ROS such as superoxide anion O2, OH ions, H2O2. Phagocytes leukocytes consumes O2---generate ROS in response to stimuli.

15. Oxygen dependent Mediated by oxidizing agents Production of reactive oxygen metabolites O2,H2O,HOCl( hypochloride ) Oxygen independent Killing through lysosomal enzymes

16. Steps Margination Diapedesis Chemotaxis Opsonization —attachment stage Engulfment stage Secretion degranulation stage Degradation stage

17. Margination the lateral movement (drift) of leukocytes toward the endothelial walls is commonly described by a well-known term called Margination

18. Margination Selectins cause leukocytes to adhere to blood vessels wall E Selectin on endothelium CD62E Pselectin platelets +endothelium CD62E,P Lselectin lymphocytes CD62L 2 nd name of selectin CD62 CD cell marker 62 is number

19. Diapedesis (emigration) T he process in which leukocyte squeezes between endothelial cells into tissue space. This almost always happens at endothelial cell borders

20. Chemotaxis WBC move towards damage cell with the help of chemoattractant Move in direction of chemicals Chemicals types Exogenous (bacteria degraded products) cell wall,chromatin molecules etc Endogenous (body make chemicals) leukotrineLTB4,InterleukinIL8, Complement systemC5a

21. chemotaxis Chemotactic substances or chemokines are Leukotrine B4 (LT-B4) C5a, C3a cytokines

22. Opsonization ---attachment Opsonization refers to the process of coating of bacteria by the opsonins The opsonin coating bacteria gets attached to the surface of phygocytes through the opsonin receptors The principle opsonins are IgG and C3b opsonin

23. Engulfment stage

24. Degranulation stage Release of lysosomal enzymes into the vesicles Oxygen dependent bactericidal mechanism Mediated by oxidizing agents Oxygen independent bactericidal mechanism mediated by lysosomal enzymes

25. THANK YOU