Constitutes 20 – 40 % of the body’s white blood cell and 99 % cells in the lymph.
Circulate continuously in the blood and lymph and migrates into the tissue spaces.
On the basis of function and cell membrane component, mainly 3 types :- B cells, T cells and NK (Natural killer cells)
1. Presented By,
Jyoti Prakash sahoo
Roll No. – 14 - AMJ – 15
Deptt. Of Agril. Biotech.
AAU, Jorhat
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Lymphocytes
September 10, 2015
2. What are these?
Constitutes 20 – 40 % of the body’s white blood cell and 99 % cells in
the lymph.
Circulate continuously in the blood and lymph and migrates into the
tissue spaces.
On the basis of function and cell membrane component, mainly 3
types :- B cells, T cells and NK (Natural killer cells)
2
September 10, 2015
3. B cells
B cells or B lymphocytes are a type of lymphocyte in the humoral
immunity of the adaptive immune system.
B cells can be distinguished from other lymphocytes, such as T cells
and natural killer cells (NK cells), by the presence of a protein on the B
cell's outer surface known as a B cell receptor (BCR) or
Immunoglobulin (Antibody).
This specialized receptor protein allows a B cell to bind to a specific
antigen.
In birds, B cells mature in the bursa of Fabricius (the name of "B" cells
comes from the name of this organ).
In mammals, immature B cells are formed in the bone marrow.
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September 10, 2015
4. Generally large “Y” shaped glycoproteins (they
have bound carbohydrates – sugars) of molecular
weight around 150,000.
There are five structural types (classes) of
antibodies in humans based on this Y-shaped
motif, these are IgA, IgD, IgE, IgG, and IgM, where
Ig stands for Immunoglobulin.
Consists of four polypeptide (protein) chains (two
heavy chains and two light chains) connected by
disulphide bonds. These chains have several
domains.
Immunoglobulins (Antibodies)
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September 10, 2015
5. What happens when B cell encounters the antigen
(Effector Cells)
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September 10, 2015
6. They can be distinguished by the presence of a T-cell receptor (TCR)
which is a unique antigen binding molecule on the cell surface.
They are called T cells because they mature in the thymus (although
some also mature in the tonsils).
T cell receptors only recognize antigen that is bound to the cell
membrane protein called MHC (Major Histocompatibility Complex).
when a antigen combined with an MHC molecule on a cell, the T Cell
differentiated into effector T cells and memory T cells.
T Cells
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September 10, 2015
7. It is a set of cell surface molecules encoded by a large gene family which controls a major part
of the immune system in all vertebrates.
The major function of major histocompatibility complexes is to bind to peptide fragments
derived from pathogens and display them on the cell surface for recognition by the
appropriate T-cells.
MHC (Major histocompatibility complex )
Heavy chain
polypeptide domains
Non-covalently
associated light chain
Heterodimers
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September 10, 2015
8. T helper cells (TH cells) assist other white blood cells in immunologic processes, including
maturation of B cells into plasma cells and memory B cells, and activation of cytotoxic T cells
and macrophages type of white blood cell that engulfs and digests cellular debris, foreign
substances, microbes.
These cells are also known as CD4+ T cells because they express the CD4 glycoprotein on
their surfaces.
These cells differentiate into effector cells that enable activation of B cells, TC cells.
Helper T Cell
Activation of a helper T cell and its roles in immunity:
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September 10, 2015
9. Cytotoxic T cells (TC cells, or CTLs) secrete cytotoxin which triggers destruction of the
pathogen's DNA or perforin which is a protein that creates holes in the pathogens plasma
membrane. The holes cause the pathogen to lyse (rupture).
These cells are also known as CD8+ T cells since they express the CD8 glycoprotein at their
surfaces.
Cytotoxic T Cell
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September 10, 2015