cells of immune system

1. Cells of the immune system
Submitted by;
Dr. Maisar Ahmad Mir
Submitted to;
Dr. Shayma K Latif

2. Cells of the immune system
Two major types of cells:
• Lymphoid cells and Non Lymphoid cells
(Myeloid cells)
Lymphoid cells:
1. B lymphocytes
2. T lymphocytes
3. Natural killer cells

3. Non lymphoid cells/Myeloid cells/Accessory
cells
• Monocytes and Macrophages
• Neutrophils
• Eosinophils
• Basophils
• Mast cells
• Dendritic cells
• Platelets
• Erythrocytes

4. Components of immune system
• Orginate in the bone marrow
• Arise from pluripotent heamtopoietic stem
cells(HSCs)
• HSCs give rise to precursor cells which are
myeloid progenitors and common lymphoid
progenitors
• Myeloid progenitors give rise to granulocytes
,macrophages, dendritic cells and mast cells
• Lymhoid precursors lymhocytes and natural killer
cells

5. T lymphocytes
• Thymus derived lymphocytes
• Arise in the bone marrow.
• Immature T cells migrate to the Thymus for
maturation / development.
• During its maturation within the thymus, T cell express
a unique antigen-binding molecule, called the T-cell
receptor (TCR) on its membrane.
• T-cell receptors can recognize antigen only when it is
bound to cell-membrane proteins called major
histocompatibility complex (MHC) molecules, called
as antigen presenting molecules.
• MHC restriction: Antigen recognition by T cell is ‘MHC
restricted’

6. T lymphocytes
• There are two well-defined subpopulations of T cells;
• T helper (TH) and T cytotoxic (Tc) cells.
• T helper and T cytotoxic cells can be distinguished
from one another by the presence of either CD4 or
CD8 membrane glycoproteins on their surfaces.
• T cells displaying CD4 generally function as T helper
cells, help in generation of HIR and CMIR
those displaying CD8 generally function as T cytotoxic
cells, responsible for CMI response against infections and
cancers.

7. B lymphocytes:
• Induce humoral immunity
• Mature B cells are distinguished from other
lymphocytes , display membrane bound
immunoglobulin(mIg) on their surface that serve
as antigen receptor.
• B cell encounters antigen and with help of TH
cells , starts proliferating (dividing), clone of B ells
with single antigen specificity are produced and
differentiated into plasma cells and memory B
cells.
• Plasma cells produce antibodies

8. Plasma cells
1. Effector cells of humoral immunity.
2. Differentiated B cells upon antigen stimulation.
3. Ovoid cells with nucleus resembling cart wheel
4. A single cell is capable of secreting from a few hundred
to more than a thousand molecules of antibody per
second.
5. Plasma cells do not divide and, although some long-
lived populations of plasma cells are found in bone
marrow, many die within 1 or 2 weeks

9. Natural killer cells:
• Large granular lymphocytes, 5-
15% in human peripheral blood
and spleen
• Innate lymphoid cells, innate
immunity against intracellular
viruses , bacteria, protozoa, kill
viral infected , bacterial infected,
cancer cells and stressed cells

10. MACROPHAGES
 Large eating cells
 Second line of cellular defense
FUNCTIONS
Phagocytosis (primary function)
Antigen processing and presentation
Secretion of cytokinins and complement proteins
Tissue repair and wound healing.

11. Neutrophils
• Predominant in blood
• First to arrive at site of infection
• Also called as Martyrs of immune system
• Major function of neutrophil is phagocytosis
• They trap and kill bacteria by releasing lytic
enzymes present in their granules
• Primary ,secondary and teritary granules

12. • Second major type of granulocytes.
• Motile phagocytic cells, less phagocytic
• Remain in blood circulation for 30 min, migrate
into tissues, majority of eosinophils located in the
intestines.
• Antiparasitic immunity: role in the defenses
against multicellular parasitic organisms,
including worms. Eosinophils can be found
clustering around invading worms.
• Rich in granules that stain intensely with red dye
‘eosin’
Eisonophils

13. Basophils
• Non phagocytic granulocytes .
• contain large granules filled with basophilic
proteins (stain blue in standard H&E staining).
• Basophils are relatively rare in the circulation,
but can be very potent.

14. Basophils
• Basophils have Fc receptor for IgE, role in allergic
reactions
• In response to binding of circulating antibodies (IgE),
basophils release their granules contents
• Histamine, one of the best known proteins in
basophilic granules, increases blood vessel
permeability and smooth muscle activity. Lipid
mediators (leukotrienes) regulate inflammation.
• Play protective role in helminths, tick infestations,
bacterial infections, degrade toxins in venoms
• Also secrete cytokines that modulate the adaptive
immune responses

15. Mast cells:
• Full of granules considered as ‘well fed cells’
• Found in wide variety of tissues, including the
skin, connective tissues of various organs, and
mucosal epithelial tissues of the respiratory,
genitourinary, and digestive tracts.
• Possess Fc receptor for IgE,role in allergy and
anaphylactic reaction (Type I hypersensitivity
reaction)

16. Dendritic cells
• Specialized APCs that can initiate
adaptive immune responses.
• Long membranous extensions that resemble dendrites
of neurons, extend & retract dynamically increasing
surface area available for browsing lymphocytes.
• Originated from myeloid progenitors (especially from
monocytes) and lymphoid progenitors of HSC
• Found in all organs except brain, parts of eye and testes
(immune privileged sites)
• Predominate in LN, skin and mucosal surfaces where
invading pathogens are most likely to be encountered.
• Discovered by Ralph Steinman in the mid 1970s –
awarded Nobel Prize in 2011.

17. Functions of DCs
1. Serve as ‘sentinel cells’ and activate innate
defences when they first encounter invaders.
2. As an APC, process exogenous antigens and
initiate adaptive immune responses.
3. Regulate adaptive immunity by determining
humoral or CMI response (Th1, Th2 cells)or
suppress or prevent an immune response
(tolerance).

18. Thank you