Ch14 Flashcards
Infection
Interaction between pathogen and body’s defense mechanisms
Antigen
Part of an organism or substance that’s recognized as non self (or self) and stimulates an immune response
Specific and non specific responses
Non specific : general and immediate same for all pathogens
specific : responds to a specific pathogen less rapid and longer lasting
To identify self and non self and types
Each type of cell has a specific molecule called an antigen on its surface with a highly specific tertiary structure which allow immune system to identify :
Pathogens
Non self material
Toxins
Abnormal cells
Limitations of immunity and how to decrease
Humans with tissue or organ transplant
Immunity system will recognize as non self material
Therefore can destroy the transplant
Therefore given immunosuppressant and choose closely related indivuals
Why is infection in fetus rare
Protected from the outside world by mother and placenta
What happens to lymphocytes that show an immune response to self antigens
Undergo programmed cell death (apoptosis)
2 types of white blood cells
Phagocytosis ; ingest and destroy material by phagocytosis
Lymphocytes ; involved in immune response
Process of phagocytosis
The phagocyte is attracted to pathogen by chemical products of it along conc gradient
The phagocyte has several receptors on cell surface membrane that attach to chemicals on surface of pathogen
Phagocytes engulf pathogen to form phagosome (vesicle)
Lysosomes within phagocyte migrate towards phagosome
Lysosomes release lysozyme into phagosome to hydrolyses bacterium
Hydrolysis products absorbed by phagocyte
T lymphocytes and what type of cells they act on
Made in bone marrow and mature in thymus gland
Cell mediated immunity
Act on :
Phagocytes that have engulfed and hydrolysed pathogen so present pathogens antigens on their cell surface membrane
Body cells invaded by viruses and also present antigens
Transplanted cells with different antigens
Cancer cells which are different from normal body cells and present antigens
Process of T lymphocytes
Pathogens invade body or taken in my phagocyte place antigens from pathogen on surface
Receptors on specific T helper cells bind to antigen
Attachment activates T helper cell to divide rapidly by mitosis and form clone of genetically identical cells
What cloned T helper cells can become
Memory cells to enable rapid response to future infections by same pathogen
Stimulate phagocytes to engulf more pathogen by phagocytosis
Stimulate B cells to divide and secrete antibody
Activate cytotoxic T cells
Cytotoxic T cells
Kill abnormal cells and body cells that are infected by pathogen
Produce protein called perforin
Makes holes in the cell surface membrane
Making it leaky so cell nonfunctional
Humoral immunity - B cells
Involves antibodies which are soluble in blood and tissue fluid
Each B cell produces specific antibody to one specific antigen
When non self antigen enters the blood there will be only one B cell that has an antibody for it (complimentary)
Process of humoral immunity
Surface antigens of invading pathogen taken up by B cells by endocytosis
B cells process antigen and presents then on surface
Helper T cell receptor attaches to processed antigen = activates B cells to divide by mitosis
Clone of plasma cells produce and secrete specific antibodies that fit antigen on pathogens surface
Some B cells develop into memory cells and some into plasma cells
2 type of cells developed from a clone
Plasma cells : secrete antibodies into blood plasma survive only for a few days responsible for immediate defense of body against infection
Memory cells : do not produce antibodies directly
Circulate the blood and tissue fluid when encountering the same antigen
Divide rapidly and develops into plasma cells and more memory cells
Long term immunity
Antibodies
Proteins with specific binding sites synthesized by B cells
Each antibody has 2 identical binding sites complementary to specific antigen
Made of four polypeptide chains
Antibodies do not destiny the antigens they only prepare them to be destroyed by diff antigens
How antibodies prepare antigens
Agglutination of bacterial cells :
Clumps of bacterial cells formed easier for phagocyte to allocate them as less spread out
Markers : stimulate phagocyte to engulf the bacterial cells and
How antibodies prepare antigens
Agglutination of bacterial cells :
Clumps of bacterial cells formed easier for phagocyte to allocate them as less spread out
Markers : stimulate phagocyte to engulf the bacterial cells and
Structure of antibodies
Binding site with a specific tertiary structure due to different amino acid sequences
Can form antigenantibody complex with on,y one type of antigen
Hinge region
Makes agglutination possible
Constant region which binds to B cells surface
What is immunity
Ability of an organism to resist an infection
Passive immunity
Introduction of antibody from an outside source
No direct contact with pathogen is needed
No memory cells produced
Active immunity
Stimulating the production of antibodies by individuals own immune system
Direct contact with pathogen and memory cells produced
Vaccination
Introduction of appropriate weakened pathogens with antigens into the body only a small amount introduced to reduce side effects
Feature of vaccination
Must be economically available
Few side effects
Means of producing storing and transporting available
Means of administering the vaccine (trained staff)
Possible to vaccinate most population
Herd immunity
When sufficiently large populations of the population has been vaccinated making it hard for pathogen to spread
Important as protects the vulnerable like babies as immunity system is weak
Why vaccination may not eliminate a disease
Fails to induce immunity in certain individuals
May develop disease before immunity levels are high
Pathogens may mutate frequently so antigens change (antigen variability)
Many varieties of a particular pathogen
Pathogens can hide inside cells or like cholera in intestine out of reach
May have objections due to ethical or religious reasons
Ethics of using vaccine
Involving use of animals cruelty
Side effects that can cause long term harm
To what extent should individuals be to accept the risks for public health
Should vaccination be compulsory
