Cell-mediated immunity is a type of immune response that involves the activation of specific immune cells to target and destroy infected or abnormal cells.
It is distinct from humoral immunity, which involves the production of antibodies to target foreign substances.
Cell-mediated immunity is important for protecting the body against infectious diseases caused by viruses and intracellular bacteria.
The immune response is initiated when antigen-presenting cells present foreign antigens to T cells, which then become activated and differentiate into effector cells that can recognize and kill infected or abnormal cells.
Cell-mediated immunity also involves the production of cytokines, which help regulate the immune response, and it is involved in the development and progression of autoimmune diseases
2. Definition
1. Cell-mediated immunity is a type of immune
response that involves the activation of specific
immune cells to target and destroy infected or
abnormal cells.
2. It is distinct from humoral immunity, which involves
the production of antibodies to target foreign
substances.
3. Cell-mediated immunity is important for protecting
the body against infectious diseases caused by
viruses and intracellular bacteria.
4. The immune response is initiated when antigen-
presenting cells present foreign antigens to T cells,
which then become activated and differentiate into
effector cells that can recognize and kill infected or
abnormal cells.
5. Cell-mediated immunity also involves the production
of cytokines, which help regulate the immune
response, and it is involved in the development and
progression of autoimmune diseases.
4. T cells
1. T cells are a type of lymphocyte involved in cell-
mediated immunity.
2. They differentiate in the thymus and are activated
when they encounter foreign antigens presented
by antigen-presenting cells.
3. Different types of T cells have different functions,
such as cytotoxic T cells that can directly kill
infected cells, helper T cells that can stimulate
other immune cells, and regulatory T cells that
can suppress immune responses.
4. T cells have specific T cell receptors on their
surface that allow them to recognize and bind to
specific antigens.
5. Dysfunctional T cells can lead to a variety of
diseases, including autoimmune disorders and
immunodeficiencies.
5. Natural killer (NK)
1. NK cells are a type of lymphocyte that can
recognize and kill infected or abnormal
cells.
2. Unlike T cells, NK cells do not require
activation by specific antigens or MHC
molecules.
3. NK cells use a variety of receptors to detect
changes in the surface of infected or
abnormal cells.
4. NK cells can directly induce apoptosis in
these cells, without the need for prior
activation.
5. NK cells play an important role in immune
surveillance, and defects in NK cell function
have been associated with various
6. Macrophages
1. Macrophages are a type of phagocyte that can
engulf and digest invading pathogens.
2. Macrophages can also act as antigen-presenting
cells (APCs), presenting antigens to T cells to
help initiate the immune response.
3. Macrophages can produce cytokines that
activate other immune cells, as well as help
promote tissue repair and healing.
4. Macrophages play an important role in both
innate and adaptive immunity, helping to
eliminate pathogens and initiate and regulate the
immune response.
5. Dysregulation of macrophage function has been
associated with several diseases, including
infections, autoimmune disorders, and cancer.
7. How T cells are
activated and
differentiate into
effector cells:
8. 1. Antigen presentation by APCs involves
processing foreign antigens into peptides
and presenting them on MHC molecules.
2. T cells recognize and bind to antigens
presented by APCs via their TCR and
require additional signals from the APC
for activation.
3. Activated T cells differentiate into effector
cells, such as helper T cells and cytotoxic
T cells, with specific functions to fight the
invading pathogen.
4. Clonal expansion occurs, where T cells
divide rapidly to generate large numbers
of effector cells to target the specific
antigen.
5. Memory T cells are formed after the
infection is cleared, providing long-lasting
immunity against future infections with the
same pathogen.
9. The role of cytokines
in regulating the
immune response
1. Cytokines activate and proliferate immune cells such
as T cells, B cells, and natural killer cells
2. Cytokines attract immune cells to sites of infection or
inflammation
3. Cytokines modulate immune cell function by
influencing differentiation, polarization, and survival
4. Cytokines regulate pro-inflammatory and anti-
inflammatory responses
5. Cytokines promote tissue repair and healing by
promoting angiogenesis and tissue repair factors such
as TGF-β and VEGF.
10. Examples of diseases that are
controlled by cell-mediated
immunity, such as viral infections and
some types of cancer.
1. Viral infections: Cytotoxic T cells and helper T
cells play a crucial role in controlling viruses.
2. Cancer: Cell-mediated immunity can recognize
and eliminate cancer cells.
3. Autoimmune diseases: Autoreactive T cells
attack self-tissue, leading to inflammation.
4. Transplant rejection: Donor tissue is recognized
as foreign, leading to T cell attack and
destruction.
11. Immune evasion strategies used by
pathogens to evade cell-mediated immunity.
Antigenic variation:
Pathogens can rapidly
change their surface
antigens, making it difficult
for the immune system to
recognize and target them.
Intracellular survival: Some
pathogens can survive and
replicate inside host cells,
evading detection by the
immune system.
Suppression of immune
response: Pathogens can
produce molecules that
suppress or modulate the
host immune response,
making it less effective in
eliminating the infection.
Destruction of immune cells:
Some pathogens can target
and destroy immune cells,
such as T cells and
macrophages, thereby
reducing the effectiveness of
the immune response.
Mimicry of host molecules:
Pathogens can produce
molecules that mimic host
molecules, which can
interfere with the normal
function of the immune
system and help the
pathogen evade detection
12. Current research and potential
therapies targeting cell-
mediated immunity.
1. Cancer immunotherapy involves boosting cell-
mediated immunity to recognize and attack cancer
cells.
2. Vaccines can stimulate cell-mediated immunity to
promote long-lasting immunity.
3. For autoimmune diseases, therapies are being
developed to modulate or suppress the immune
response to prevent tissue damage.
4. Therapies to prevent transplant rejection involve
suppressing the recipient's immune response,
such as through drugs that target T cell activation
or cytokine signaling.
5. Advancements in understanding cell-mediated
immunity are leading to new therapies for a variety
of diseases.
