Morphology, functions and potential application of T Lymphocytes

Morphology, functions and potential
application of T Lymphocytes
GROUP 3


Outline
•Introduction
•Morphology of T Lymphocyte
•Functions of T Lymphocyte
•Potential application of T Lymphocytes


Introduction
T lymphocyte is a type of lymphocyte (a subtype of white blood cell) that
plays a central role in cell-mediated immunity

In this immunofluorescence image, a cytotoxic T cell
(blue). A patch of signaling molecules (pink). Lytic
granules (red), the microtubule cytoskeleton (green)

Scanning electron micrograph of a human
T lymphocyte (also called a T cell) from the
immune system of a healthy donor. Credit:
NIAID


Morphology of T Lymphocytes
•T-Lymphocytes are a type of white blood cells that play a
role in cell-mediated immunity.(1)
•Blood T and B lymphocytes are indistinguishable by light
and electron microscopy

•The difference between T lymphocytes and B lymphocytes
are difference of diameter.


Morphology of T Lymphocytes
•T cells are about 7-8 micrometers
•Small amount of light blue cytoplasm
•Coarsely clumped chromatin
•Nucleus is round oval in shape


Morphology of T Lymphocytes
The surface of each T cell also displays thousands of
identical T cell receptors (TCRs).
There are two types of T cells that differ in their TCR:
◦ Alpha/beta (αβ)  T cells
◦ Gamma/delta  (γδ) T cells


Morphology of T Lymphocytes
Alpha/beta (αβ) T cells.
Their TCR is a heterodimer of an
alpha chain with a beta chain


Morphology of T Lymphocytes
Gamma/delta (γδ) T cells.
Their TCR is also a
heterodimer of a gamma
chain paired with a delta

chain.


Morphology of T Lymphocytes
Most of the T cells in the body belong to one of
two subsets. These are distinguished by the
presence on their surface of one or the other of
two glycoproteins designated:
• CD4
• CD8


Morphology of T Lymphocytes

CD8+T cell

CD4+T cell
DR.TV.Rao MD


Types Of T Cells
 Helper T cells.
 Suppressor T cells.
 Cytotoxic T cells.
 Memory T cells.


Helper T Cells
 Also known as CD4+ T cells.
 ¾ of T cells.

 Two major types: Th1 and Th2.


Helper T Cells
 Stimulation of cytotoxic and suppressor T cells.
 Stimulation of B cells’ growth, differentiation
to form plasma cell clones. (Th1)
 Activation of Macrophage system. (Th2)
 Feedback stimulation effect on themselves.


Helper cells that
have not become
activated.


Helper T Cells
Cytotoxic T cells and B cells cannot react to the
antigens without the “permission” of helper T
cells.


Suppressor T Cells
Also known as regulatory T cells.
Suppress function of cytotoxic and helper T cells.
→ shut down (turn off) those immune system
cells when an infection has been brought under
control.

Suppressor T Cells
Prevent the excessive damge to the healthy
surrounding tissue.
→Prevent damage to body itself.
→Immune tolerance.
Regulatory cells along with helper cells.


Cytotoxic T Cells
•CD8-cytotoxic T cell: killer cell
•Direct attack on infected cell
•Perforin: hole-forming protein
•Destroying cancer cells; heart
transplant cells or other cells
foreign to body


Cytotoxic T Cells
Recognition

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Cytotoxic T Cells
Activation


Cytotoxic T Cells
Releasing perforin
and granzyme

Perforin

Cytotoxic T Cells
Forming of perforin on
surface of infected cell


Cytotoxic T Cells
Hole-forming and entering of
granzyme


Cytotoxic T Cells
Cell death


Memory T cells
To be activated by antigens but do not enter in circulation,
remain in lymphoid organs
A small fraction of active CD8+ T cell persist to generate pool
of a long-lived memory.
Self-renew and protect against infection.
The basis of vaccination.