Cells of immune system
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Transcript of Cells of immune system
PRESENTED
BY
TANIYA.M.S
MSC . BIOTECHNOLOGY
Cells of the Immune System-I
1. Originated from
Bone Marrow (BM)
2. Two major lineages:
- Lymphoid
- Myeloid
3. NK cells
- Large Granular
Lymphocytes (LGL)
Cells of Adaptive immunity
1. Lymphocytes are the key players of the adaptive
immunity.
2. Lymphocytes are able to specifically recognize and
respond to diverse antigens.
=> Antigen receptors on lymphocytes
=> Specificity Diversity & Memory
3. Lymphocytes are classified into three major groups:
- B cells => Antibodies => Humoral immunity
- T cells => Multiple subtypes => Cell-mediated immunity &
Regulate other immune cells
- NK cells => Innate immunity
Lymphocytes
Specific receptores (TCR and BCR)
Based on site of differentiation and on receptors:
T cells and naturall killers T - in thymus - (TCR)
B cells – bone marrow - (BCR)
(no cell surface specific receptors – NK cells)
Classes of Lymphocytes
1. B cells => Plasma cells
=> Abs
2. T cells:
- T helper cells
- T cytotoxic cells
- T regulatory cells
-T memory cells
-T NK cells
=> suppress immune
responses
3. NK cells
4. Subtypes in each class
Thymus derived cells
T lymphocytes
Most important players of specific immunity
Direct effectors and regulators of activity of other cells
Produced in bone marrow: not mature T cell – prothymocyte
Migrates in thymus - thymocyte, where TCR are produce.
T cells and leave thymus and enter to ciruculation
Contain surface receptors TCR
CD3, CD4 or CD8
- CD4 T cell
2/3 of all T cells containging CD3
CD4 cell surface molecule
– recognise part of MHC II
molecule that is not part
of peptid binding site
Functionally – helper
- CD8 T cells
1/3 of all T cells containing CD3
CD8 cell surface molecule – recognise part of MHC I molecule that is not designated to bind peptids
Functionally : Tc cytotoxic – eliminate virus or i.c.bacteria infected cells
Ts supressor – increase and control reactions of specific immunity
Cells produced in bone marrow only
B - lymphocytes
Not all cells produced in bone marrow migrate to
thymus
Some differentiate in bone marrow further and are
precursors of cells producing immunoglobulins
B lymphocytes – B cells – synthetise
immunoglobulin, that is then situated on the cell
surface as BCR.
Differenciated mature B cell synthetises and
secretes immunoglobulines
B cells
Plasma cells
Memory cells
B1 cells
Regulatory cells
- Plasmatic cells
Derived from terminally differentiated B cells
Produce and secrete immunoglobulines
In the momente, when they start to produce and secrete Ig, they stop to use immunoglobuline molecule as BCR
They are bigger and have bigger metabolic activity
Produce large amounts of Ig
survive 30 days
NK cells – natural killers
5% - 10% periferal blood lymphocytes
do not have markers (receptors) as T cells
(CD3, TCR) and B cells (Ig)
kill cells infected by viruses and tumor cells
without previous sensibilisation
Null cells
A null cell is a large granular lymphocyte
Without surface markers or membrane-associated proteins from B lymphocytes or T lymphocytes.
Natural killer cells are usually null cells with surface marker CD 16
Attack pathogens and abnormal cells.
Members of null cells are NK cells.
In 75% of the cases of ALL, the lymphocytes are neither B nor T-cells and are called Null cells.
Innate immune cells are
classified as following:
- Monocyte/Macrophage
- Dendritic cell (DC)
- Polymorphonuclear
granulocyte (PMN;
Neutrophil, Eosinophil,
Basophil)
- Mast cell
Classes of innate immune cells
WBC’s
Five Types
Classified according to the presence or absence of granules and the staining characteristics of their cytoplasm.
Leukocytes appear brightly colored in stained preparations, they have a nuclei and are generally larger in size than RBC’s.
Type of WBC’s
Granulocytes—have large granules in their cytoplasm
Neutrophils
Eosinophils
Basophils
Polymorphonuclear Granulocytes: Neutrophils
1. Comprise over 95% of
granulocytes
2. Short-lived (2-3 days)
3. Multi-lobed nucleus
4. Kill pathogens by
phagocytosis & releasing
cytotoxic substances.
Granuloctyes
Neutrophils
Stain light purple with neutral dyes
Granules are small and numerous—course appearance
Several lobes in nucleus
65% of WBC count
Highly mobile/very active
Diapedesis—Can leave blood vessels and enter tissue space
Phagocytosis (eater), contain several lysosomes (janitor)
Neutrophils are a type of phagocyte.
During the beginning phase of inflammation, the first-responders of inflammatory cells to migrate towards the site of inflammation.
They migrate through the blood vessels, then through interstitial tissue,
following chemical signals such as Interleukin-8 (IL-8), Leukotriene B4 in a process called chemotaxis.
They are the predominant cells in pus, accounting for its whitish/yellowish appearance
Granulocytes
Eosinophils
Large, numerous granules
Nuclei with two lobes
2-5% of WBC count
Found in lining of respiratory and digestive tracts
Important functions involve protections against
infections caused by parasitic worms and
involvement in allergic reactions
Secrete anti-inflammatory substances in allergic
reactions
Eosinophils play a crucial part in the killing of
parasites (e.g., enteric nematodes) because their
granules contain a unique, toxic basic protein and
cationic protein
Granulocytes
Basophils
Least numerous--.5-1%
Diapedesis—Can leave blood vessels and
enter tissue space
Contain histamine—inflammatory chemical
Basophils are one of the least abundant
cells in bone marrow and blood(occurring
at less than two percent of all cells).
Like neutrophils and eosinophils, they have
lobed nuclei; however, they have only two
lobes, and the chromatin filaments that
connect them are not very visible.
Agranulocytes,
mononuclear leukocytes,
with a one-lobed nucleus.
They are characterised by the absence of
granules
2 types of agranulocytes in the blood
circulation are lymphocytes and monocytes.
A third type of agranulocyte, the
macrophage is formed monocytes leave the
circulation and differentiate into
macrophages.
Agranulocytes
Lymphocytes
Smallest WBC
Large nuclei/small amount of cytoplasm
Account for 25% of WBC count
Two types—T lymphocytes—attack an infect
or cancerous cell, B lymphocytes—produce
antibodies against specific antigens (foreign
body)
Agranulocytes
Monocytes
Largest of WBCs
Dark kidney bean shaped nuclei
Highly phagocytic
ROLES
Replenishing resident macrophages under normal states,
In response to inflammation signals, monocytes can move to sites of infection in the tissues and divide/differentiate into macrophages and dendritic cells to elicit an immune response.
Half of them are stored in the spleen
Monocytes are usually identified in stained smears by their large kidney shaped or notched nucleus.
These change into macrophages after entering into the tissue spaces.
Macrophages
Big eaters “( MΦ)
That engulf and digest cellular debris, foreign substances, microbes and cancer cells in a process called phagocytosis .
Beyond increasing inflammation and stimulating the immune system,
macrophages also play an important anti-inflammatory role and can decrease immune reactions through the release of cytokines.
Macrophages that encourage inflammation are called M1 macrophages, whereas those that decrease inflammation and encourage tissue repair are called M2 macrophages
Phagocytosis
Dendritic cells (DCs)
Accessory cells
Dendritic cells were first described by Paul
Langerhans in the late 19th century.
Antigen-presenting cells of the mammalian
immune system.
Main function -process antigenmaterial
and present it on the cell surface to the t cells.
Act as messengers between the innate and
the adaptive immune systems .
Dendritic cells are present in those tissues that are in contact with the external environment,
Eg. skin and the inner lining of the nose, lungs, stomachand intestines.
also be found in an immature state in the blood.
Once activated, they migrate to the lymph nodes where they interact with T cells and B cells to initiate and shape the adaptive immune response.
At certain development stages they grow branched projections, the dendrite that give the cell its name .
Immature dendritic cells are also called veiled cells, as they possess large cytoplasmic 'veils' rather than dendrites
REFERENCE
Campbell, Neil A., Reece Jane B., Biology(6th edition), Pearson Education, Inc., 2002
Delves, P.J., Martin, S. J., Burton, D. R. and Roit I.M. Roitt's Essential Immunology(11th edition), Blackwell Publishing, 2006,
Ernst J. D. and Stendahl O., (editors), Phagocytosis of Bacteria and Bacterial Pathogenicity, Cambridge University Press, 2006,
Hoffbrand, A.V., Pettit, J.E. and Moss, P.A.H., Essential Haematology (4th edition), Blackwell Science, 2005
Thank you