Communicable Diseases 4.1 Flashcards
What are opsonins ?
-a type of antibody
-they are proteins that bind to the antigen on a pathogen to enhance the ability of phagocytic cells to bind and engulf the pathogen
What is a neutrophil ?
-the most common phagocyte
-they have a multi-lobed nucleus
-they are manufactured in the bone marrow
-they are shorted lived
-a large amount of them will be released as a result of infection
How do neutrophils act to destroy pathogens ?
-neutrophil binds to the opsonin attached to the antigen of the pathogen
-the pathogen is engulfed by endocytosis forming a phagosome
-lysosomes fuse to the phagosome and release lytic enzymes into it
-after digestion the harmless products can be absorbed into the cell
Define a neutrophil
A type of white blood cell that engulfs foreign matter and traps it in a large vacuole (phagosome) which fuses with lysosomes to digest the foreign matter
Define an antigen presenting cell ?
A cell that isolates the antigen from a pathogen and places it on the plasma membrane so that it can be recognised by other cells in the immune system
Define what a cytokine is
Hormone-like molecules used in cell signalling to stimulate the immune response
What are macrophages?
-larger than neutrophils
-manufactured in bone marrow and travel in the blood as monocytes before settling in the body tissue, many found in lymph nodes
What is the role of macrophages?
-play a role in initiating the specific response to invading pathogens
-when it engulfs a pathogen it does not fully digest it
-the antigen from the surface of the pathogen is saved and moved too a special protein complex on the surface of the cell (the cell becomes an antigen-presenting cell)
-through this other cells in the immune system can recognise the antigen
-special protein complex ensures the antigen-presenting cell is not mistaken as a foreign cell and attacked
What do antigen-presenting cells do?
They move around the body where it can come into contact with specific cells that can activate the full immune response
It increases the chances that an antigen will come into contact with them
What is clonal selection ?
Selection of a specific B or T cell that is specific to the antigen
What do T helper cells do?
They release cytokines (chemical messengers) that stimulate the B cells to develop and stimulate phagocytosis by the phagocytes
What do T killer cells do?
They attack and kill host-body cells that display the foreign antigen
They do this by making holes in the cell surface membrane using perforins
What do T memory cells do?
They provide long-term immunity
What do T regulator cells do?
They shut down the immune response after the pathogen has been successfully removed.They are also involved in preventing autoimmunity.
What are B and T lymphocytes?
-white blood cells that have a large nucleus and specialised receptors on their plasma membranes.
-both are made by bone marrow stem cells
-but B cells mature in the bone marrow
-and T cells mature in the thymus
What are the two types of cells that B lymphocytes develop into?
-plasma cells
-B memory cells
What are plasma cells?
-they circulate in the blood
-they manufacture and release antibodies
-they are responsible for immediate defence
What are B memory cells?
-don’t produce antibodies directly
-they remain in the body for a number of years and act as immunological memory
What are interleukins?
Signalling molecules that are used to communicate between different white blood cells
What is cell signalling ?
The communication between cells in the specific immune response.
The communication is achieved through the release of hormone-like chemicals called cytokines.
In order to detect a signal the target cell must have a cell surface receptor complementary in shape to the shape of the signalling molecule.
What are three examples of communication using cytokines?
-macrophages release monokines. Some monokines attract neutrophils (by chemotaxix-movement of cells towards a particular chemical.) Others stimulate B cells to differentiate and release antibodies
-T cells and macrophages release interleukins which can stimulate the clonal expansion(proliferation) and differentiation of B and T cells
-many cells can release interferon, which inhibits virus replication and stimulates the activity of T killer cells
What is clonal expansion?
An increase in the number of cells by mitotic cell division
What is an antigen?
-usually proteins or glycoproteins in the plasma membrane of the pathogen
-they will be recognised by the body as foreign by the immune system they are usually a marker on the surface of a cell
-this will stimulate the production of antibodies
What is an antibody?
-an immoglobulins- complex proteins produced by the plasma cells in the immune system
-they are released in response to an infection
- they have a region with a specific shape that is complementary to that of a particular antigen
-they attach to antigens and neutralise them making them harmless
-our immune system must manufacture one type of antibody for every antigen that is detected
What do opsonins do?
-they are a group of antibodies that bind to the antigens on a pathogen
-they act as binding sites for phagocytic cells so that these can more easily bind and destroy the pathogen