Cell recognition and the immune system Flashcards
Describe the principle of cell recognition
-In order to defend an organism during invasion by foreign material, lymphocytes must be able to distinguish between the bodys own cells and molecules ( self cells) and ones that are foreign (non self cells)
-All cells have specific molecules on its surface used to identify it, including proteins
- These proteins have enormous variety and a highly specific tertiary structure
- These can identify pathogens, toxins, abnormal body cells and cells from other organisms of the same species
How does the mechanism of cell recognition impact those who have had tissue or organ implants?
-Immune system will recognise the transplant as non self even though they have come from an organism of the same species
- It therefore attempts to destroy the transplant
- Doctors therefore match a transplant as close to a recipent as possible
- Immnosupressant drugs are also administered
What is a non specific defence mechanism give e.g
- Response is immediate and the same for all pathogens e.g physical barriers (skin) or phagocytosis
What is a specific defence mechanism give e.g
- Response is slower and different for all pathogens e.g a cell mediated response ( T lymphocytes) or a humoural response ( B lymphocytes)
Why is there a time lag between exposure to the pathogen and the bodys defences bringing it under control?
- When the infection occurs, the one type of lymphocyte which has complementary proteins to the pathogen present is stimulated to divide to build up its number to a level of which it can be effective in destroying the pathogen
Describe the process of phagocytosis
Chemical products of pathogens, or dead, abnormal cells act as attractants , causing phagocytes to move towards the pathogens
Phagocytes have several receptors on their cell surface membrane that recognise, and attach to the chemicals on the surface of the pathogen
They engulf the pathogen to form a vesicle called a phagosome
Lysosomes move towards the vesicle and fuse with it
Enzymes in the lysosomes called lysozymes destory the ingested bacteria by hydrolysis of cell walls
The soluble products from the breakdown of the pathogen are absorbed into the cytoplasm of the phagocyte
Define immunity
The ability of an organism to resist infection by protecting against disease causing micro-organisms or their toxins that invade their bodies, involves the recognition of antigens
Define antigen
Any part of an organism or substance that is recognised as non self by the immune system and stimulates an immune response, triggers an antibody
Give examples of antigens
Usually proteins that are part of the cell surface membranes or cell walls of invading cells such as micororganisms or abnormal body cells such as cancer cells
What is a lymphocyte?
One type of white blood cell which are produced by stem cells in the bone marrow
What is a B lymphocyte ( B cell)?
They mature in the bone marrow
Associated with the humoural immunity( antibodys present in bodily fluids e.g blood plasma)
What is a T lymphocyte ( T cell)?
Mature in the thymus gland
Associated with cell-mediated immunity
How are T lymphocytes able to distinguish between invader cells and self cells?
- Phagocytes that have engulfed and hydrolysed a pathogen present some of a pathogens antigens on their own cell surface membrane
- Body cells infected by a virus present some of the viral antigens on their own cell surface membrane
- Transplanted cells from organisms of the same species present different antigens on their cell surface membrane due to a difference in genetic material
-Cancer cells are different from normal body cells and present antigens on their cell surface membranes
What is an antigen presenting cell?
Cells that present forigen antigens on their surface
Describe the process of the cellular response
Pathogens invade body cells or are taken in by phagocytes
The phagocyte places antigens from the pathogen on its cell surface membrane
Receptors on a specific helper t cell fit exactly onto these antigens
This attachment activates the T cell to divide rapildy by mitosis and form a clone of genetically identical cells
The cloned T cells have functions ( diff flashcard)
