Immune response Flashcards
Physical barriers to infection
- Skin which is a tough physical barrier consisting of keratin.
- Stomach acid (hydrochloric acid) which kills bacteria.
- Gut and skin flora – natural bacterial flora competes with pathogens for food and space.
Non-specific responses of the body to infection include:
- Inflammation
- Lysozyme action
- Interferon
Inflammation (Non-specific response)
histamines released by damaged white tissues cause vasodilation which increases the flow of blood to the infected area and increases permeability of blood
vessels. As a result of that antibodies, white blood cells and plasma leak out into the infected tissue and destroy the pathogen.
Lysozyme action
lysozyme are enzymes found in secretions such as tears and mucus which kill bacterial cells by damaging their cell wall.
Interferons
prevent viruses spreading to uninfected cells by stopping protein synthesis in viruses.
Phagocytosis (Non-specific response)
- Phagocyte is attracted to the pathogen by chemical products of the pathogen. It moves towards it on a concentration gradient
- The surface receptors on the phagocyte attach to chemicals on the surface of the pathogen
- Invagination occurs and a phagosome forms
- Lysosomes release lysozymes into the phagosome, hydrolyse the bacteria
- The hydrolysis products of the bacterium are absorbed by the phagocyte
Specific Immune Response
is antigen specific and produces responses specific to one type of pathogen only
What does the Specfic immune response rely on?
B cells & T-cells
Where are B cells/ Plasma cells found
mature in the bone marrow and are involved in the humoral response.
Where are T cells found
s move from the bone marrow to the thymus gland where they mature, and are
involved in cell mediated response.
Memory cells
Cells which replicate themselves when exposed to an invading pathogen and remain in the lymph nodes for decades searching for the same antigen. Results in a faster immune response
B cells
B effector or plasma cells are antibody producing cells.
T helper cells
Stimulate B cells and T killer cells to divide.
T cytotoxic cells
Release toxins that bind to and kill foreign cells and abnormal cells in the body.
Reservoir
The place where the pathogen is usually found.
Suppressor cells
turn off immune response, e.g. turning off antibody production.
Cell-mediated immune response
- Uses T-lymphocytes which are produced in the bone marrow and mature in the thymus gland.
- Once matured T-lymphocytes circulate the body in the blood until it meets an antigen it has the receptor site for.
- It is then stimulated to divide by mitosis many times forming clones.
Describe the process of cell mediated immunity (immunity that does not result in the production of antibodies).
- Phagocytosis of foreign material by phagocyte.
- Foreign antigens from material are presented on phagocyte.
- Specific T-helper lymphocyte (Th) binds to foreign antigen (clonal selection)
- Attachment causes Th cell to undergo mitosis (clonal expansion).
Cloned T cells can:
- become memory cells for rapid future response.to same pathogen.
- stimulate phagocytes to engulf via phagocytosis.
- stimulate B cells to divide and release antibodies (humoural response)
- activate cytotoxic T cells (Tc) cells to kill.
What can the cloned T-lymphocytes do after clonal expansion has taken place in the cell mediated response?
become memory cells for rapid future response.to same pathogen.
stimulate phagocytes to engulf via phagocytosis.
stimulate B cells to divide and release antibodies (humoural response)
activate cytotoxic T cells (Tc) cells to kill.
Which type of immunity are T-lymphocytes mainly involved in?
Cell Mediated Immunity (they are just used to stimulate B-cells in humoural immunity)
Where can non-self antigens be found that T-lymphocytes may bind to?
- The surface of an antigen presenting cell (phagocyte)
- Body cells invaded by a virus may present viral antigens.
- Transplanted cells from organ donors.
- Cancer cells
- Toxins produced by pathogens.
Can T-lymphocytes bind to non-self antigens floating around freely in the blood?
No - they can only bind to foreign antigens that have been presented on an antigen presenting cell e.g. phagocyte.
How do cytotoxic T lymphocytes (Tc) protect against disease?
They kill cells infected by pathogens or cancerous cells.
They produce a protein called perforin.
Perforin creates holes in target cell membranes, which kills the cell.
Where do T-lymphocytes mature?
In the thymus