Cellular defense involves specialized immune cells that respond when chemical and physical barriers are breached by foreign agents. These cellular defense cells include neutrophils, macrophages, and natural killer cells. Neutrophils are the most abundant white blood cell and form part of the innate immune system. They undergo chemotaxis and phagocytosis to migrate to infected sites and ingest microbes. Macrophages also phagocytose debris, microbes, and damaged cells. Natural killer cells provide rapid responses to virally infected cells through cytotoxic granule mediated apoptosis.

1. CELLULAR DEFENCE

2. CELLULAR DEFENCE
If an infections agent is not successfully repelled by the chemical
and physical barriers than special type of cells involve in the
encounter of foreign cells.
These cell are the part of innate immunity and whose number
increases when any foreign particle enters.

3. CELLS OF CELLULAR DEFENSE
1. NEUTROPHILS CELLS
2. MACROPHAGES CELLS
3. N.K.C.(NATURAL KILLER CELLS)

4. 1.NEUTROPHILS CELL
• Neutrophils (also known as neutrocytes) are the most abundant type of
granulocytes and the most abundant (40% to 70%) type of white blood
cells in most mammals.
• They form an essential part of the innate immune system.
• They are formed from stem cells in the bone marrow .
• These cell have multilobe nucleus and their cytoplasmic granules is not
stained by acidic or basic granules.

6. FUNCTION OF NEUTROPHILS
 They are the most important phagocytic cells.
 Neutrophils undergo a process called chemotaxis via
amoeboid movement, which allows them to migrate toward
sites of infection or inflammation.
 They are the cells which exhibits extravasation.

7. PHAGOCYTOSIS
 Neutrophils are phagocytes, capable of ingesting
microorganisms or particles. For targets to be
recognized, they must be coated in opsins a process
known as antibody opsonisation.

9. EXTRAVASATION
 Leukocyte extravasation, less commonly called
diapedesis, is the movement of leukocytes out of the
circulatory system and towards the site of tissue damage or
infection.
 This process forms part of the innate immune response.

11. 2.MACROPHAGES
 Macrophages are a type of white blood cell, of the immune system,
that engulfs and digests cellular debris, foreign substances, microbes,
cancer cells, and anything else that does not have the type of proteins
specific to healthy body cells on its surface in a process called
phagocytosis. These large phagocytes are found in essentially all
tissues.
 They take various forms (with various names) throughout the body
(e.g., histiocytic, Kuffer cells, alveolar macrophages, microglia, and
others), but all are part of the mononuclear phagocyte system.

12. Cell Name Anatomical Location
Adipose tissue macrophages Adipose tissue (fat)
Monocytes Bone marrow/blood
Kuffer cells Liver
Sinus histiocytes Lymph nodes
Alveolar macrophages (dust cells) Pulmonary alveoli of lungs
Tissue macrophages (histiocytes)
leading to giant cells
Connective tissue
Microglia Central nervous system
Hofbauer cells Placenta
Intraglomerular mesangial cells Kidney
Osteoclasts Bone

13. FUNCTION OF MACROPHAGES
 Macrophages are professional phagocytes and are highly specialized in
removal of dying or dead cells and cellular debris. This role is
important in chronic inflammation

14. 3. NATURAL KILLING CELLS
 Natural killer cells or NK cells are a type of cytotoxic
lymphocyte critical to the innate immune system.
 The role NK cells play is analogous to that of cytotoxic T
cells in the vertebrate adaptive immune response.
 NK cells provide rapid responses to viral-infected cells.

15. FUNCTION OF NK CELLS
 Catalytic granule mediated cell apoptosis:-
 NK cells are cytotoxic; small granules in their cytoplasm contain proteins,
such as perforin and proteases known as granzymes.
 Upon release in close proximity to a cell slated for killing, perforin forms
pores in the cell membrane of the target cell, creating an aqueous
channel through which the granzymes and associated molecules can enter,
inducing either apoptosis or osmotic cell lysis