Phagocytosis

Phagocytosis

• 2.
  Definition ❖ Phagocytosis formsthe second line of defence ❖ In Greek “phagein” means to eat “cyte” means the cell and “osis” means the process ❖ “Phagocytosis is a process of ingestion and uptake of microbes and other substances by a cell” ❖ It is used by Phagocytic cells of our immune system to get rid of the pathogens which have breached first line of defence Antimicrobial substances Phagocytosis Natural killer cells Inflammation and Fever Second line of Denfence
• 3.
  Phagocytes ❖ The cellsthat perform phagocytosis are known as Phagocytes ❖ The main types of phagocytes of immune system are 1. Monocytes 2. Macrophages 3. Neutrophils 4. Dendritic cells ❖ Function of these phagocytes is to destroy the engulfed pathogens ❖ These phagocytes are equipped with certain intracellular compartments such as lysosomes which contains microbicidal substances (Lysozymes, Nucleases, Proteases, Lipases, H2O2 etc,.) Dendritic cells : These are special group of phagocytic cells, since besides performing the processing of engulfed pathogen they well present the same antigen (which is a part of Adaptive immune system)
• 4.
  Mechanism of Phagocytosis
• 5.
  Steps 1. Recognition :Recognition of antigens will take place by Pathogen Recognition Receptors (PRRs) present on the plasma membrane of phagocytes which will recognize specific molecular patterns on the invading microbes called Pathogen Associated Molecular Patterns (PAMPs) 2. Ingestion : The phagocyte will extends its plasma membrane to form finger like projections called pseudopodia around the adhered pathogen 3. Formation of Phagosome : The membrane after surrounding the pathogen will pinches off from its surface to form a sac known as “phagosome” or “phagocytic vesicle” to internalize the pathogen
• 6.
  4. Formation ofphagolysozome : The phagocytic vesicle will now fuse with one or more lysosomes present in the cytoplasm to form larger structure called “Phagolysosome” 5. Digestion or Killing : The phogolysosome has lower pH (acidic environment) and variety of microbicidal enzymes which will contribute in the destruction of internalised microbe 6. Formation of residual bodies : Once the killing and digestion of the engulfed microbial cell happens only indigestible materials remain in sac and this sac containing indigestible materials is called “Residual body”
• 7.
  7. Elimination orExocytosis : The formed residual body will move towards the cell boundary and discharges its contents outside the cell That's all folks.. Thank you!!!