H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 12: Diseases and Infection
Assignment 12D: Understand how the human body
responds to diseases and infections
Introduction
In this report, the cell-mediated and humoral immune responses will be
evaluated in terms of their relevance, significance, advantages and
disadvantages, and strengths and weaknesses.
Named diseases and pathogens will be used for each immune response to detail
the progression of the disease in the body in relation to the speed and specificity
of the response.
Cell-mediated response
The cell-mediated response is the response of T cells to a foreign antigen and
below is an overview of the process:
1- T cells recognise antigen-presenting cells after phagocytosis
2- Specific T helper cells with receptors complementary to the specific
antigen bind to it, becoming activated and dividing by mitosis to form
clones that:
Stimulate B cells for the humoral response
Stimulate cytotoxic T cells to kill infected cells by
producing perforin that causes holes in the membrane
Stimulate phagocytes to engulf pathogens by
phagocytosis
This response is linked to and helps the humoral response as the T cells in this
response cause B cells for the humoral response to become activated.
An example of a disease that is fought against by the cell-mediated response is
tuberculosis, which is caused by the bacterium, Mycobacterium tuberculosis.
First off, when this tuberculosis bacterium enters the body, it is engulfed and
destroyed by a phagocyte using phagocytosis- see Figure 1 below. Following this,
T cells identify the tuberculosis bacterium as the process of phagocytosis cause
it to have its antigens presented on its surface- refer to Figure 2 below. Specific T
helper cells with complementary CD4 receptors bind to the tuberculosis antigen
and this activates the T helper cells to divide by mitosis, forming clones. These
clones that are produced differentiate into different types of cells that stimulate
B cells for the humoral response, cytotoxic T cells to release perforin (a protein
that causes holes in the membrane) to kill infected tuberculosis cells and
phagocytes to engulf tuberculosis bacteria by phagocytosis. Some clones also
differentiate into memory cells which allow for the immune system to recognise
the tuberculosis bacterium and its complementary antigen if encountered in the
body again. These clones fight to remove the tuberculosis pathogen from the
body by destroying it and breaking it down in infected cells.
Figure 1- Diagram of phagocytosis process (4)
, H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 12: Diseases and Infection
Figure 2- Diagram of cell-mediated response (8)
In relation
to this disease’s progression, the cell-mediated response shows a delayed
response in individuals (6). This is significant as it means that an individual can
experience a range of symptoms associated with tuberculosis since the cell-
mediated response takes a while to develop protection against the tuberculosis
pathogen. Therefore, the progression of this disease can be quite rapid, infecting
cells in the body, and increasing the severity of symptoms.
Additionally, this response is highly specific to the tuberculosis antigen as the
receptors on T cells are complementary to the tuberculosis antigen. These
receptors on T cells allow them to identify the tuberculosis antigen on the
tuberculosis bacterium. This is significant as the specificity of this response
protects the body against future invasion of this tuberculosis bacterium since
memory cells are produced because of this cell-mediated response.
This response is relevant to the tuberculosis bacterium as complementary
receptors are made to bind to T cells which attach to the antigen on the
tuberculosis bacterium (6). This leads to the destruction of the tuberculosis
bacterium in the body, defending the body against tuberculosis. Moreover, the
cell-mediated response is a significant response to fight against diseases such as
tuberculosis as it prevents the spread of intracellular infections by destroying
intracellular pathogens from infecting cells in the body.
In terms of strengths and weaknesses, the strengths of the humoral response
include the following:
- Produces complementary receptors on T cells against antigens on
pathogens, destroying pathogens
- Enables immunological memory as memory cells are produced
- Can be used to respond to a variety of intracellular pathogens
On the other hand, this response has the following weaknesses:
- Slow response
- T cells could attack the body’s own cells due to failure to recognise self-
tissue
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 12: Diseases and Infection
Assignment 12D: Understand how the human body
responds to diseases and infections
Introduction
In this report, the cell-mediated and humoral immune responses will be
evaluated in terms of their relevance, significance, advantages and
disadvantages, and strengths and weaknesses.
Named diseases and pathogens will be used for each immune response to detail
the progression of the disease in the body in relation to the speed and specificity
of the response.
Cell-mediated response
The cell-mediated response is the response of T cells to a foreign antigen and
below is an overview of the process:
1- T cells recognise antigen-presenting cells after phagocytosis
2- Specific T helper cells with receptors complementary to the specific
antigen bind to it, becoming activated and dividing by mitosis to form
clones that:
Stimulate B cells for the humoral response
Stimulate cytotoxic T cells to kill infected cells by
producing perforin that causes holes in the membrane
Stimulate phagocytes to engulf pathogens by
phagocytosis
This response is linked to and helps the humoral response as the T cells in this
response cause B cells for the humoral response to become activated.
An example of a disease that is fought against by the cell-mediated response is
tuberculosis, which is caused by the bacterium, Mycobacterium tuberculosis.
First off, when this tuberculosis bacterium enters the body, it is engulfed and
destroyed by a phagocyte using phagocytosis- see Figure 1 below. Following this,
T cells identify the tuberculosis bacterium as the process of phagocytosis cause
it to have its antigens presented on its surface- refer to Figure 2 below. Specific T
helper cells with complementary CD4 receptors bind to the tuberculosis antigen
and this activates the T helper cells to divide by mitosis, forming clones. These
clones that are produced differentiate into different types of cells that stimulate
B cells for the humoral response, cytotoxic T cells to release perforin (a protein
that causes holes in the membrane) to kill infected tuberculosis cells and
phagocytes to engulf tuberculosis bacteria by phagocytosis. Some clones also
differentiate into memory cells which allow for the immune system to recognise
the tuberculosis bacterium and its complementary antigen if encountered in the
body again. These clones fight to remove the tuberculosis pathogen from the
body by destroying it and breaking it down in infected cells.
Figure 1- Diagram of phagocytosis process (4)
, H.
BTEC L3 EXTENDED DIPLOMA IN APPLIED SCIENCE
Unit 12: Diseases and Infection
Figure 2- Diagram of cell-mediated response (8)
In relation
to this disease’s progression, the cell-mediated response shows a delayed
response in individuals (6). This is significant as it means that an individual can
experience a range of symptoms associated with tuberculosis since the cell-
mediated response takes a while to develop protection against the tuberculosis
pathogen. Therefore, the progression of this disease can be quite rapid, infecting
cells in the body, and increasing the severity of symptoms.
Additionally, this response is highly specific to the tuberculosis antigen as the
receptors on T cells are complementary to the tuberculosis antigen. These
receptors on T cells allow them to identify the tuberculosis antigen on the
tuberculosis bacterium. This is significant as the specificity of this response
protects the body against future invasion of this tuberculosis bacterium since
memory cells are produced because of this cell-mediated response.
This response is relevant to the tuberculosis bacterium as complementary
receptors are made to bind to T cells which attach to the antigen on the
tuberculosis bacterium (6). This leads to the destruction of the tuberculosis
bacterium in the body, defending the body against tuberculosis. Moreover, the
cell-mediated response is a significant response to fight against diseases such as
tuberculosis as it prevents the spread of intracellular infections by destroying
intracellular pathogens from infecting cells in the body.
In terms of strengths and weaknesses, the strengths of the humoral response
include the following:
- Produces complementary receptors on T cells against antigens on
pathogens, destroying pathogens
- Enables immunological memory as memory cells are produced
- Can be used to respond to a variety of intracellular pathogens
On the other hand, this response has the following weaknesses:
- Slow response
- T cells could attack the body’s own cells due to failure to recognise self-
tissue
