Chapter 11: Immunity Flashcards
Define the term phagocyte.
Specialised white blood cells that engulf and
destroy pathogens. There are two types:
neutrophils and macrophages.
State where phagocytes are produced.
Bone marrow
Define the term phagocytosis.
The process by which phagocytes engulf
and destroy pathogens.
Outline the process of phagocytosis.
- Phagocyte moves towards pathogen via chemotaxis
- Phagocyte engulfs pathogen via endocytosis to form a phagosome
- Phagosome fuses with lysosome forming a phagolysosome
- Lysozymes digest pathogen
- Products of pathogen hydrolysis absorbed by the phagocyte or
released into the cytoplasm
Define the term immune response.
The body’s response to ‘non-self’ antigens. It
consists of a non-specific phase involving
neutrophils and macrophages, and a specific
phase involving T and B lymphocytes.
What is an antigen?
A chemical present on the surface of a cell
that induces an immune response.
What are antigen presenting cells (APCs)?
Any type of immune cell which displays
parts of a pathogen (antigens) on its
surface to elicit an immune response.
What is meant by the term self-antigen?
Antigens present on an organism’s cells
that are tolerated by their own immune
system. They induce antibody formation
in other organisms.
What is meant by the term non-self antigen?
Foreign antigens that originate from
outside the body and induce an immune
response.
Describe the structure and function of T
lymphocytes.
● Mature in the thymus gland
● Many specific receptors and immunoglobulins on surface
● Four main types of T lymphocyte:
○ T helper - bind to antigens on antigen-presenting cells and secrete interleukins ○ T killer - secrete perforin, destroying pathogens with a specific antigen ○ T memory - provide immunological memory ○ T regulatory - suppress other immune cells to prevent autoimmune disease
Describe the structure and function of B
lymphocytes.
● Mature in the bone marrow
● Many specific receptors and immunoglobulins on surface
● Three main types of B lymphocyte:
○ Plasma cells - produces antibodies specific to a particular pathogen ○ B effector - divides to form plasma cells ○ B memory - provide immunological memory
Define the humoral immune response.
Immunity regulated specifically by the
production of antibodies. Associated with
B lymphocytes.
State the role of plasma cells.
Production of antibodies specific to a
particular pathogen.
Outline the process of the cell-mediated response.
Complementary T helper lymphocytes bind to foreign antigens on
antigen-presenting cell. T cells undergo clonal expansion.
Four main types of T lymphocytes produced:
● T effector cells
● T killer
● T helper cells
● T memory cells
Outline the process of the humoral response.
- Complementary T helper lymphocytes bind to foreign antigens on
antigen-presenting T cells - Cytokines released that stimulate the clonal expansion of
complementary B lymphocytes - B lymphocytes differentiate into plasma cells
- Plasma cells secrete antibodies with complementary variable region
to antigen. Antibodies destroy the pathogen
State the potential impact of Leukemia on blood cell
count and its consequence.
May cause uncontrolled division of bone marrow stem
cells, increasing the number of red and white blood
cells in the bloodstream. Leukaemia cells are typically
immature and can disrupt the blood clotting cascade
and specific immune responses.
State the effect of bacterial infection on T lymphocyte
count.
T lymphocyte count increases due to the
cell-mediated immune response.
A greater number of T cells will circulate the
body even after the infection has subsided.
State the effect of HIV on T cell count.
HIV destroys specific T cells. A decrease
in normal levels of T cells is expected
over time in individuals with HIV.
Compare the primary and secondary immune
responses.
● Primary immune response - initial response when a pathogen is
first encountered. A small number of antibodies are produced
slowly.
● Secondary immune response - pathogen encountered for a
second (third, fourth…etc.) time. Immunological memory gives a
rapid production of a large number of antibodies.
What is the function of memory cells?
They remain in the body for a long time following
an infection and provide long-term immunity. If
the organism encounters the same pathogen in
the future, they can divide rapidly to provide an
effective secondary immune response.
Define the term autoimmune disease.
A condition in which the immune system fails
to distinguish between self and non-self
antigens, so attacks and destroys healthy
body tissue. Examples include arthritis and
lupus.
How does autoimmune disease occur?
T cells with self antigens are not destroyed
during the maturation process. If these cells
become active they will launch an immune
response on self cells, leading to cell
damage.
What is myasthenia gravis?
An autoimmune disease that causes skeletal muscle
weakness due to the production of antibodies which
damage nicotinic acetylcholine receptors at the
neuromuscular junction. Motor neurons cannot be
stimulated therefore muscles receive no impulses. This
leads to atrophy of muscles.
Describe the structure of an antibody
● Y-shaped. Two ‘light chains’ bonded to two
longer ‘heavy chains’ by disulfide bridges
● Binding sites on variable region of light
chains have specific tertiary structure
complementary to an antigen
● The rest of the molecule is known as the
constant region
