specific cellular defences against pathogens Flashcards
Describe what lymphocytes are and how they work
Lymphocytes are the white blood cells involved in the specific immune response.
Lymphocytes respond to specific antigens on invading pathogens.
Lymphocytes have a single type of membrane receptor which is specific for one
antigen.
Describe how a clonal population of lymphocytes are formed
Antigen binding leads to repeated lymphocyte division resulting in the
formation of a clonal population of identical lymphocytes
what is an antigen
Antigens are molecules, often proteins located on the surface of cells that trigger a specific immune response.
State the two types of lymphocytes
B lymphocytes and T lymphocytes
Describe the role of B lymphocytes
B lymphocytes produce antibodies against antigens and this leads to the destruction of the pathogen.
State the role of antibodies
Antibodies are Y-shaped proteins that have receptor binding sites specific to a
particular antigen on a pathogen. Antibodies become bound to antigens, inactivating the pathogen. The resulting antigen-antibody complex can then be destroyed by phagocytosis
Explain how an allergic reaction occurs
B lymphocytes can respond to antigens on substances that are harmless to the body, eg pollen. This hypersensitive response is called an allergic reaction.
Describe the role of T lymphocytes
T lymphocytes destroy infected body cells by recognising antigens of the pathogen on the cell membrane and inducing 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. The remains of the cell are then removed by phagocytosis.
what is an apoptosis
programmed cell death
Explain how an autoimmune disease occurs
T lymphocytes can normally distinguish between self-antigens on the body’s own cells and non-self-antigens on infected cells.
Failure of the regulation of the immune system leads to T lymphocytes responding to self-antigens. This causes autoimmune diseases.
State what memory cells are
Some of the cloned B and T lymphocytes survive long-term as memory cells.
explain the secondary response
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.
During the secondary response, antibody
production is greater and more rapid than
during the primary response.
Explain how the human immunodeficiency virus (HIV) affects the body.
The human immunodeficiency virus (HIV) attacks and destroys T lymphocytes. HIV
causes depletion of T lymphocytes which leads to the development of AIDS
