infectious disease - immunity Flashcards
inflammation response
Blood vessels around an infected area are supplied with extra blood, making the area red and swollen. This leads to an increase in temperature in the region, leading to possible pathogen death.
mast cells
release of histamines in damaged tissue increasing the permeability of blood vessels, which allows phagocytes to leave the blood vessels and move into the damaged tissue.
mast cells
release of histamines in damaged tissue increasing the permeability of blood vessels, which allows phagocytes to leave the blood vessels and move into the damaged tissue.
phagocyte
A type of white blood cell (macrophage or neutrophil) capable of engulfing and
absorbing bacteria and other foreign particles.
phagocytosis
Phagocytes change their shape to flow around bacteria and other foreign particles. The phagocytes completely enclose the invading bacteria within their cell, where they are broken up by cellular enzymes.
lymph system
Bacteria and other microbes are picked up in the lymphatic fluid and trapped inside lymph nodes, where they can be attacked and destroyed by phagocytes.
cell death to seal off pathogen
Involves infected cells, or macrophages that have engulfed pathogens undergoing apoptosis. In doing so, both the cell and pathogens inside die.
Innate immune system – 2nd line of defence
The innate immune system provides non-specific resistance that attempts to destroy any invading pathogens.
antibodies
Proteins produced by B cells in response to specific antigens.
Lymphocytes
White blood cells that are responsible for adaptive immune responses.
Memory B cells
accumulate in the spleen and lymph system for a long period of time. If another exposure to the same antigen occurs the required antibody will be produced quickly, and in large amounts.
antibodies
proteins naturally produced by B cells in response to antigens. They therefore play a critical role in the immune systems defence against infection and disease.
antibody structure
Each antibody consists of four polypeptides – two heavy chains and two light chains joined to form a “Y” shaped molecule.
The heavy chain and lower end of the light chain are conserved in all antibodies.
The 2 variable regions of the light chain are identical antigen-binding sites and attach to identical antigens.
antibody function
Neutralisation – Antibodies bind to antigen molecules on the surface of pathogens.
Agglutination – Antibodies bind to antigens on the surface of host cells and form antibody-antigen complexes which activate phagocytes and the complement cascade leading to destruction of the cell and pathogens.
types of T cells
killer
helper
memory
supressor
Killer T cells (Tc cells)
Attack and destroy foreign cells, infected host cells and abnormal ‘self’ cell, including tumor cells.
Helper T cells (Th cells)
Become activated by APC (including activated B cells). They stimulate the cloning of specific B and T cells by the secretion of interleukins.
Memory T cells
Remain in the body and reactivate quickly with subsequent exposure to the same antigen.
Suppressor T cells
Stop the immune response when the antigen is destroyed.
interleukin
One of a group of related proteins made by white blood cells to regulate immune responses.
Major histocompatibility complex (MHC)
Cell surface proteins essential for the acquired immune system to recognise antigens
innate immunity
Innate (natural) immunity is present from birth, unlike acquired immunity which is ‘learnt’ from exposure to pathogens.
Innate immunity provides a non-specific, immediate response to pathogens.
The cells involved recognise a limited number of antigens
Innate immunity retains no ’memory’ of exposure to a pathogen
provides no ongoing protection from continued exposure to the same microbe.
(NBMEN) White blood cells involved in innate immunity:
Monocytes (which develop into macrophages and
dendritic cells)
Neutrophils
Eosinophils
Basophils
Natural killer cells
Monocytes, macrophages and dendritic cells
develop from monocytes after they move from the bloodstream into tissues. This occurs in response to infection.
As macrophages and dendritic cells mature, they increase in size and produce enzyme filled granules.
When they phagocytose bacteria or other foreign cells, they release the enzymes that kill the ‘invaders’.
Both macrophages and dendritic cells are antigen presenting cells (APCs) and they therefore participate in acquired immunity.
Neutrophils
most common type of white blood cell in the bloodstream.
Like macrophages, they are phagocytes.
produce neutrophil extracellular traps (NETs), which are networks of fibres that bind and trap pathogen, preventing further spread.
neutrophils are not antigen presenting cells and therefore play no role in acquired immunity.
Eosinophils
Eosinophils also possess enzyme filled granules which help destroy bacteria that they phagocytose.
Their primary role, however is to target foreign cells that are too large to engulf, for example internal parasites.
They attach on mass to the parasites and immobilise it.
Basophils
Basophils do not carry out phagocytosis.
They contain histamine filled granules.
When released in response to antigen detection the histamine increases blood flow to damaged tissues resulting in inflammation and the attraction neutrophils and eosinophils.
Natural Killer cells (NK cells)
primarily involved in the initial defence against viral pathogens and cancer cells
cytotoxic.
They contain cytoplasmic granules filled with perforin and proteases.
Once a NK cell detects a ‘non-self’ cell it attaches to it and releases these cytotoxic molecules causing the lysis, and death of the target cell.
acquired immunity
During the first exposure to an antigen, the adaptive immune system must ‘learn’ how to attack and destroy a pathogen.
Once a ‘memory’ of a pathogen has been obtained, a secondary exposure will result in a much more rapid response. The individual has acquired immunity.
clonal selection theory
first proposed by the Australian scientist Macfarlane Burnet in 1957.
It explains the process by which a specific antigen only activates its counter-specific B cell to multiply and produce specific antibodies to the antigen.
