cell recognition and the immune system Flashcards
what is immunity?
is when the body is better prepared to deal with a pathogen usually after it has already been infected once.
what are the two types of lymphocytes?
T lymphocytes are involved in cell-mediated responses
B lymphocytes are involved in humeral response.
what is an antigen?
a molecule usually a protein that induces an immune response, it is a molecule that is recognised as non-self.
what are the key things that the proteins can detect?
pathogens, non self cells, toxins, abnormal body cells.
how do lymphocytes recognise cells that belong to the body?
in the foetus lymphocytes are constantly colliding with other cells- where infection is rare as t is protected by the mother (placenta) therefore they will collide with almost exclusively body cells. the cells that react to the body cells die or are suppressed. the only ones remaining are those that might fit foreign material and therefore only respond to foreign material.
in adults lymphocytes are found in the bone marrow. if any of these lymphocytes produce an immune response they undergo programmed cell death (apoptosis)
what are the two types of white blood cell?
phagocytes and lymphocytes.
what is a phagocyte and what does it do?
a phagocyte is a type of white blood cell (e.g. a macrophage) engulf and destroy a pathogen via phagocytosis.
how does a phagocyte work?
firstly the phagoyste recognises the foreign antigens on a pathogen. the phagocyte then engulfs the pathogen to form a vesicle called a phagosome. lysosomes then love towards the vesicle and fuse with it. enzymes called lysozmes are present within the lysosome, these break down the pathogen via by the hydrolysis of their cell walls. the phagocyte then presents the pathogens antigens.
what is a B lymphocyte?
otherwise known as a B cell are so called because they mature in the bone marrow. they are associated with humeral immunity
what is a T lymphocyte?
T cells are formed in the thymus gland are associated with a cell meditated response.
what is cell meditated immunity?
lymphocytes respond to an organisms own cells that have been infected by non-self material from a different material and also cells that are genetically different.
how can a T lymphocyte tel the difference between invader cells?
phagocyte that have presented a pathogens antigens on their own cell membranes
body cells present some of the viral antibodies on their membrane if they have been infected
transplanted cells have different antigens
cancer cells are different body cells and present antigens on their membrane.
what are the stages of T lymphocytes in rospose to a pathogen?
when a pathogen is taken in by phagocytes or invade a cell, the T helper cell attaches its self to the antigen which it id specific to and then begins to rapidly clone genetically identical T cells
the clone cells develop into memory cells, stimulate phagocytes to engulf the pathogens, stimulate B cells to divide and recreate their antibody, activate cytotoxic T cells which release perforin.
how do cytotoxic T cells kill infected cells?
the produce a protein called perforin that makes holes in the cell surface membrane this means that the cell be ones freely permeable to all substances and the cell dies as a result.
what is humeral immunity?
humoral immunity involves antibodies which are soluble in the blood and tissue fluid. there are many different B cells each producing a specific antibody that is specific for a individual antigen.
what happens when a B cell detects a antigen?
when a b cell detects a specific antigen, the antigen enters the B cell via endocytosis and gets presented on its surface. the Thcell attaches to this b cell and orders it to divide this forms an identical B cell of which produce the antibody that is specific to that antigen- called clonal selection
what are monoclonal antibodies?
as each clone produces one specific antibody
what are plasma cells?
b cells that secrete antibodies into the blood - these cells can only survive for a few days but each make around 2000 antibodies every second
what are memory cells?
b cells responsible for secondary immune response. when they encounter an antigen at a later date they dede rapidly into plasma cells or more memory cells
what are antibodies?
antibodies are proteins with specific binding sites synthesised by T cells. each antibody has two identical binding sites which are complementary to a specific antigen, mass variation can occur as they are made of proteins.
what is the structure of an antibody?
antibodies consist of 4 polypeptide chains. the chains of one pair are long and are called heavy chains and the others are called light. each antibody has a specific binding site that forms an antigen-antibody complex. binding site is different and so os therefore called the variable region, the rest of the antigen is known as the constant region.
how do antibodies lead to the destruction of pathogens?
agglutination of bacterial cells. clumps of bacterial cells are formed
thy serve as markers to that stimulate phagocytes to engulf the bacterial cell.
what are the functions of antibodies in medicine and science.
targeting medication to specific cell types by attaching a therapeutic drug to an antibody
- e.g. monoclonal antibodies that are specific to a cancer cell are produced and then given to a patient and then attach themselves to the receptors on the cell, they attach to the surface of the cancer cells and block the chemical signals that stimulate uncontrolled growth.
- lead to fewer side affects
medical diagnosis
pregnancy testing
what is indirect monoclonal antibody therapy?
where a cytotoxic drug or a radioactive substance is attached to the monoclonal antibody so that when it attaches to the cancer cells it kills them.
