KA6 Specific cellular defences against pathogens Flashcards
What are lymphocytes?
White blood cells involved in the specific immune response
Lymphocytes respond to specific antigens on invading pathogens
What is an antigen?
Antigens are molecules, often proteins located in the surface of cells (or pathogens) that trigger a specific immune response
What causes division of lymphocytes?
Each lymphocyte has a single type of membrane receptor which is specific to one type of antigen
Antigen binding leads to repeated lymphocyte division resulting in the formation of a clonal population of identical lymphocytes
What are B lymphocytes?
B lymphocytes produce antibodies against antigens
This leads to the destruction of the pathogen
What are antibodies?
Antibodies are Y- shaped proteins that have receptor binding sites specific to a particular antigen on the pathogen
How do antibodies prevent pathogens from causing further infection?
Antibodies become bond to antigens, inactivating the pathogen. The resulting antigen- antibody complex can then be destroyed by phagocytosis.
How can B lymphocytes cause an allergic reaction?
B lymphocytes can respond to antigens on substances that are harmless to the body, eg pollen. This hypersensitivity is called an allergic reaction
What are T lymphocytes?
T lymphocytes destroy INFECTED BODY CELLS by recognising antigens of the pathogen on the cell membrane and inducing apoptosis
What is apoptosis?
Programmed cell death
What is the process of apoptosis?
T lymphocytes attach onto infected cells and release proteins
These proteins diffuse into the infected cells causing production of self destructive enzymes which cause cell death
How are the remains of cells removed?
Phagocytosis
What is a self antigen?
A self antigen is on a persons own body cells so that the immune system does not launch an attack
What does failure of the regulation of the immune system lead to?
T lymphocytes attack the body’s own cells. This causes autoimmune diseases such as type 1 diabetes and rheumatoid arthritis
What do some cloned B and T lymphocytes survive long term as?
Memory cells
How do memory cells respond to a secondary exposure to the same antigen?
When a secondary exposure to the same antigen occurs, these memory cells rapidly give rise to a new clone of specific lymphocytes
These destroy the invading pathogens before the individual shows symptoms
