antigens Flashcards
what are antigens ?
antigens are molecules that generate an immune response
what are antigens complementary to ?
antigens are complementary to the receptors of the cells that perform an immune response i.e T helper cells
where are antigens located ?
antigens are located on the surface of all cells including cells in the human body
what are foreign antigens ?
antigens that belong to cells not usually found in the body
what do foreign antigens do ?
stimulate the immune system
what are 3 examples of things that have foreign antigens ?
-pathogens
- toxins
- cancerous cells
what kind of response is phagocytosis ?
a cellular response which is non-specific
what kind of cells are also a part of the cellular response ?
T-cells
what are T-helper cells activated by ?
T-helper cells are activated by specific antigens that are complementary to receptors presented on an APC and not antigens detached from cells in the body fluids
how do T- helper cells respond ?
by producing cytokines
what are cytokines ?
chemicals that activate other cells of the immune system
- which also attract cells of the immune system which increases the immune response
what is the humoral response to do with ?
antibodies
how long do B memory cells approximately last ?
5 years
explain the humoral response ?
B-cells are activated by cytokines and complementary antigens
- activated B-cells undergo mitosis and differentiation which is called clonal selection
- some B-cells become B plasma cells that make antibodies and some cells become B memory cells that last up to 5 years in the blood
where are all lymphocytes made ?
in the bone marrow
where do t-cells mature?
in the thymus
what does APC stand for ?
antigen presenting cell
what are APC ?
any cell that presents a non-self antigen on its cell surface membrane
what will T-cells only respond to ?
T-cells will only respond to antigens which are presented on the APC and not antigens that are detached from cells and within body fluids i.e blood
what can T-helper cells differentiate into ?
-some remain as T cells and activate B cells
-some stimulate macrophages to peform more phagocytosis
-some become memory cells for that shaped antigen
-some become cytotoxic T cells
what do cytotoxic T cells do ?
cytotoxic T-cells destroy abnormal or infected cells by releasing a protein called perforin which embeds into cell membranes and makes a pore so that any substances can enter or leave the cell which causes cell death
where are cytotoxic t cells most common ?
in viral infections because viruses infect body cells
at is meant by active immunity ?
when you have been previously exposed to a pathogen so that when you get exposed again large numbers of antibodies can be produced so rapidly that the pathogen is destroyed before any symptoms occur
What is the cell-mediated response?
The response involving T cells and body cells
Example of APC
- Infected body cells will present viral antigen on their surf
- macrophage which has engulfed and destroyed a pathogen
- cells of a transplanted organ will have different shaped antigen on their surface compared to your self- cell antigens
- cancer cells
First stage of the cell mediated response ?
- once a pathogen has been engulfed and destroyed the antigens will be presented on the cell surface membrane which is called an APC
Second stage of the cell mediated response ?
Helper t cells have receptors that are complimentary to the antigens on the apc
Third stage of the cell mediated response
Once attached this activates the t helper cells to divide by mitosis and replicate to make large numbers of clones
4 th stage of the cell mediated response
Cloned t helper cells differentiate into different cells
- some remain as helper T cells and activate b lymphocytes
- some stimulate macrophages to perform phagocytosis
- some become memory cells for that antigen
- some become cytotoxic T cells (killer t cells )
