Introduction to T cells in the immune system

1. Introduction to T cells
T cells are a type of white blood cell that play a key role in the immune
system's defense against infections and diseases. They are responsible
for identifying and destroying infected cells while also coordinating the
overall immune response.
by Adesh tholmbre

2. Activation of T cells
1 Antigen Recognition
T cells become activated when their T cell receptor recognizes a specific
antigen, often presented by antigen-presenting cells.
2 Co-stimulation
Co-stimulatory signals, such as interactions with co-stimulatory molecules,
are required to fully activate T cells.
3 Clonal Expansion
Activated T cells undergo clonal expansion, producing a large population of
effector T cells with identical antigen specificity.

3. Effector functions of T cells
Cytokine Secretion
Activated T cells can
release cytokines to
modulate the immune
response, promoting
inflammation or
coordinating immune cells.
Direct Killing
Certain T cells, like
cytotoxic T cells, directly kill
infected or abnormal cells
to limit the spread of
pathogens.
Helping B Cells
Helper T cells provide
essential signals to activate
and guide B cells in
producing antibodies
against specific pathogens.

4. Cytotoxic T cells and their role in
killing infected cells
1 Target Recognition
Cytotoxic T cells
recognize and bind to
infected cells
displaying specific
antigens on their
surface.
2 Perforin Release
Upon recognition,
cytotoxic T cells
release perforin,
creating pores in the
target cell's
membrane.
3 Granzyme
Secretion
Granzyme proteins
are then delivered into
the target cell through
the pores, inducing
cell death.

5. Helper T cells and their role in
coordinating immune responses
Antigen Presentation
Helper T cells recognize
antigens presented by
antigen-presenting cells,
triggering their activation.
Cytokine Release
Activated helper T cells
release cytokines to
stimulate and direct the
immune response against
specific antigens.
B Cell Activation
Helper T cells provide
crucial signals to activate B
cells and support antibody
production.

6. Memory T cells and their role in
long-term immunity
Antigen Recall
Memory T cells
"remember" specific
pathogens, allowing for a
rapid and targeted
response upon re-
exposure.
Longevity
Memory T cells persist
for an extended period,
providing long-term
immune protection and
enhanced response to
familiar threats.
Rapid Activation
Upon re-encounter with
a known antigen,
memory T cells quickly
expand and initiate a
potent immune
response.

7. Regulation of T cell responses
Regulatory T Cells
Regulatory T cells play a vital
role in preventing excessive
immune responses and
maintaining immune
tolerance.
Tolerance Induction
T cells contribute to the
establishment of peripheral
tolerance to self-antigens,
protecting against
autoimmunity.
Immune Suppression
Some T cells possess
suppressive functions,
regulating immune reactions
to prevent damage to healthy
tissues.

8. Conclusion and summary
T cells Key Players in Immunity
Cytotoxic T Cells Targeted Cell Killing
Helper T Cells Immune Response Coordination
Memory T Cells Long-term Immune Protection