2. Content
• Introduction
• Cells of immune system
• Hematopoiesis
• Phagocytic cells
• Granulocytes
• Lymphocytes
• Conclusion
3. Introduction
The immune system is spread throughout the body
and involves many types of cells, organs, proteins,
and tissues. Crucially, it can distinguish our tissue
from foreign tissue — self from non-self. Dead and
faulty cells are also recognized and cleared away by
the immune system.
4. Cells of immune system
• WBCs are the principle cells of immune system
formed hematopoietic stem cell by the process of
hematopoiesis. Hematopoiesis occurs in yolk sac
during 1st week of gestation. After 3rd month of
gestation, hematopoiesis occurs in liver and spleen
of fetus and after birth, it occurs in bone marrow.
5. Hematopoiesis
Hematopoiesis is the process by which mature blood
elements of all lineages are derived from a common
pluripotent stem cell.
6.
7. Monocyte
Structure
• Mono nuclear phagocytic cells
• It measures 12 - 15 micro meter
• Single lobed kidney shaped nucleus
• It accounts 2-8% of leukocytes
Life span
• Circulates in blood for 8 hours them moves
to specialized tissue to form macrophage
Function
• Helps in antigen processing and presenting
• Releases cytotoxins
• Cytotoxicity
8. Macrophage
• Monocyte migrates to tissue and differentiate to
form macrophage. During this process it includes
some changes
1. Cells enlarge to 5-10 folds
2. Intracellular granules increases in number and
complexity
3. Increase phagocytic ability
4. Produces higher level of hydrolysis enzyme &
cytokine
Function
• Phagocytosis
• Antigen presentation to The cell
• Secretion of IL-1 ,IL-6, IL-12, TNF -alpha to activate
inflammatory response
9. Neutrophils
Structure
• It is 11-14µm in diameter with multilobed nucleus with
granules in cytoplasm.
• It constitutes 50-70 % of total circulating WBC and remains
for 7-8 hours in blood and then migrates to tissues
• Life span is 3-4 days.
• Also known as polymorphonuclear (PMN) lymphocytes
Function
• Phagocytic role in acute inflammatory response.
• It is the first immune cell to responds in inflammation.
• It express higher levels of defensins than macrophages
10. Basophil
Structure
• It constitutes only 1% of leukocytes. They are
circulating cells
• Nucleus is bilobed or S shaped
• It contains large, irregular basophic granules
• They are non phagocytic cells
• Granules contain histamine, heparin, serotonin, and
other hydrolysis enzyme
Function
• It plays a role in immunity against parasites
• Provide anaphylactic and atope allergic reaction
• On degranulation release histamine which cause
adverse symptoms of allergy
11. Eosinophil
Structure
• Form small portion of peripheral blood 1-5%
• They are bilobed and granulated cytoplasm
• They are mobile and can move to the site of action.
• They phagocytose poorly but degranulate promptly
in the presence of chemotactic factors and when
bound Ig G & Ig E is crossed linked by antigen.
Function
• Granules contain various hydrolysis enzymes that kill
parasites which are too large to be phagocytosed by
neutrophils
• Provide allergic inflamation
12. Dendritic cells
Structure
• Large, motile, weakly phagocytic, antigen
presenting cells
• That possess several elongated pseudopodia or
processes that resembles dendrites of nerve cell
• They comprise about 1%of the cell in secondary
lymphoid organs and these cells are found in
different location
Function
• They have major function of presentation of
antigen toTHcells
• They express high levels of class II MHC molecules
• Very little role in phagocytosis
13. Lymphocytes
• Lymphocytes are small, round cells found in peripheral blood, lymph,
lymph nodes, lymphoid organs and in tissues.
• Lymphocytes represent 20-45% of total cells in peripheral blood and
99% of total cells in lymph and lymph node.
• According to size lymphocytes are divided into small (5-8µm),
medium (8-12µm) and large (12-15µm).
• Depending on life span lymphocytes are classified into short lived (2
weeks) and long lived (3 years or more or even lifelong).
• Broadly lymphocytes are divided into three sub-populations, on the
basis of function and cell membrane components.
14. B lymphocyte
• The name B-cell is derived from its site
of maturation and differentiation in
Bursa of fabricius in Birds. In adult
human B- cell originates and mature in
Bone marrow.
• Morphologically B- cells are
indistinguishable from T-cells.
• B-cells are identified by their surface
protein ie. Immunoglobulin or antibody
which serves as receptor for antigen.
15. Surface receptors on B cell
• B220 (CD45): marker for B-cells and their precursor
• MHC-II: permits B-cells to function as APC.
• CR1 (CD35) and CR2 (CD21): complement receptor
• FcγRII (CD32): receptor for IgG antibody
• CD40: interacts with CD40 ligands on surface of TH cells.
• B7-1 (CD80) and B7-2 (CD86): interacts with CD28 and CTLA-4 on TH cells.
16. Functions of B lymphocyte
• Antibody production against specific target antigen
• acts as APC and present antigen to The cell
• provides signal for T cell activation
17. T lymphocyte
• T-cells originate in bone marrow and mature and
differentiate in thymus. The name T- cells is
derived from its site of maturation.
• All T-cells contains T- cell receptor (TCR) on its
surface. TCR is specific and recognize MHC bound
antigen.
• All T- cells expresses an antigen binding TCR and
CD2 and CD3 glycoprotein on their cell
membrane.
• Most of the T-cells are distinguished on the basis
of CD4 and CD8 glycoprotein receptor on their
cell membrane.
18. Sub population of T cell
T helper cells
• TH cells are activated by recognition of antigen on MHC-II on
APCs. Ie. MHC-II restricted.
• When antigen binds on TCR of CD+ T –cells, it is activated and
divides into memory cell and effector cells. Effector TH cells
secretes various cytokines which helps in B-cell activation for
production of antibodies.
T cytotoxic cells
• Tc cells are activated by recognition of antigen on MHC-I on
altered self cell such as tumor cell or virus infected cells.. Ie.
They are MHC-I restricted.
• When antigen binds on TCR of CD8+ cells, it is activated and
divides into clones of memory cell and effectors cells. Effector
Tc cells is known as cytotoxic T-lymphocytes (CTL) which kills
virus infected cell or tumor cells.
19.
20. T suppressed cells
• Ts-cells helps to suppress humoral and cell mediated immunity.
Functions
• Helps B- cell maturation, expression and antibody production
• Helps in recruitment and activation of mononuclear phagocytic cells.
• Helps in recruitment and activation of specialized cytotoxic T- cells (TCL)
in antiviral response.
• Secretes cytokines which is responsible for growth and differentiation of
T- cells, monocytes, macrophages etc
• Helps in regulation of immune reactions.
21. Natural killer cells
• Natural Killer (NK) cells are large
granular lymphocytes (LGL)
present in small proportion in
spleen and peripheral blood.
• Unlike T-cell and B-cell, NK cell
lacks specific antigen receptor.
• They are called as natural killer
cell because they do not require
activation in order to kill tumor
cells or virus infected cells.
22. functions of NK cells:
• Provide antitumor immunity
• Provide antiviral immunity
• provide antibody dependent cell mediated
cytotoxicity (ADCC).
• secretes cytokines
23. Conclusion
• Immune system possesses diverse cells and organs to
confer immunity to the body.
• The whole system is an intricate network of these
cells and organs
• Hematopoiesis generates the various blood cells
required by the body and the location of the
hematopoiesis varies initially but finally becomes
constant with age and bone marrow becomes the key
location for the process.
