IMMUNE SYSTEM Flashcards
(24 cards)
DEFENCE MECHANISMS
NON-SPECIFIC:
- cells
- Chemicals and physical barriers that are present at birth (innate)
SPEICIFIC
- activated by the presence of microbes or microbial products in the body.
- collection of organs, cells & chemicals that generate cells & antibodies for targets
ANTIGENS
- cells or substances stimulate an immune response
- come from antibody generating
- antigens = toxins, chemicals, bacteria, viruses or other substances from outside of the body
NON-SPECIFIC DEFENCE
- epithelial barriers
- phagocytes
- antimoircobial chemcials
- inflammatory reponse
- immunological surveillance
EPITHELIAL BARRIER
intact skin and mucous membrane
- bacteria
- Sebum and sweat contain antibacterial & antifungal substances
- epithelial membranes
- hairs in the nose
- urine flow and vaginal secretion
- Epithelia produce antibacterial secretions which are often acidic
PHAGOCYTES
- neutrophils & macrophages
- migrate to the site of inflammation and infection (chemotaxis)
- engulf and destroy foreign cells
- antigenic material and damaged cells & debris
- white blood cells phagocytosing yeast cells
- neurophils activated and phagocytosing = destory themselves & target
MACROPAHGES: - specialised defence cells
- longer life span than neutrophils
- Activate the immune system response for infection
- phagocytosing an antigen, displaying it on the cell surface to stimulate T cells
- produce substances = promoting inflammatory repsone = neurophils, including fever & healing
ANTIMICROBIAL CHEMICALS
hydrochloric acid (concentration in gastric juice kills most swallowed microbes) (some meds = reduction to acidity, make person more susceptible to gastrointestinal infections)
lysozyme (antibacterial enzyme) (found in granulocytes, tears & other body fluids) (destroys bacterial cell walls)
(doesn’t affect viruses or other pathogens)
saliva
- secreted in the mouth
- Washing awayy food debris could encourage bacterial growth
- contaisn antibodies lymozyme & buffers to neutrilised bacteiral acids = tooth decay
interferons
- produce & release local tissue by T cels, macrophaages & virus infected body cells
- reduce the spread of viruses to healthy body cells
complements
- system of 20 protein found in blood and tissue
- activated immune complexes & by forigen sugars on bacterial walls = phagocytosis
- acts chemoattractant gaining phagocytic cells to area of infection
antibodies:
- Protective protein synthesised by plasma cells
- bidn to & destory antigens
- found in bodily fluids
- coat membrane exposed to the external environment
INFLAMMATORY RESPOSNE
- physiological response to tissue damage & resulting in local changes
- purpose: protective & isolating, inactivating, removal of pathogens, and tissue healing can happen
- signs of inflammation:
- redness
- heat
- swelling pain
- a wide range of triggers include:
> temperatures
> trauma
> corrosive chemicals
> absorption
> autoimmunity
> infection - harful pathogen = removed & conditions for healing are optimised
ACUTE INFLMMATION
short duration
events of acute inflammation are:
- increased blood flow
- accumulation of tissue fluid
- migration of leukocytes (white blood cells)
- increased core temp
- formation of pus (suppuration)
FEVER
IMMUNOLOGICAL SURVEILLANCE
- natrual killers cells are lymphocytes
- patrol the body looking for abormal cells
abnormal cells include:
> virus-infected - mustated cells = maligment
- Abnormal host cells often display markers on their membranes, which the NK cells recognise as abnormal.
NK cells are particularly good for pre-cancerous cells and for viruses.
ADAPTIVE/SPECIFIC DEFENCES - IMMUNITY
B CELLS: humoral immunity (antibody)
T CELLS: cells immunity
SPECIFIC: directed against one antigen
MEMORY: immunological memory generated
TOLERANCE: recognising markers on host cells
TOLERANCE: healthy body (host) cells display markers so they are ignored. Non-self cells have different kinds of markers. Sometimes T cells are unable to recognise self cells, resulting in an autoimmune response.
B AND T CELLS
- lymphcytes cirulcate the lymphatic system and other tissue & blood
- B, T cells NK cells = lymphocytes
- B & T cells Carry antigen recognition molecules
T CELLS
- thymus gland = production of hormone thymosin
- Thymosin promotes the maturation of T cells
- A mature T cell recognises one type of antigen
- T cells provide cell-mediated immunity
B CELLS
- B cells are & produced in bone marrow
- produce antibodies (immunolgoblin)
- proteins desgined to bind to & destory antigens
- B cells target one specific antigen
- B cells provide antibody-mediated immunity
CELL-MEDIATED IMMUNITY
-mature T cells released from the thymus into circulation
- Antigens re-enter the body
- T cells can’t detect free antigens in body fluids
- The cells that present antigens are antigen-presenting cells (APCs).
- T cells are now activated
ANTIGEN-PRESNETING CELLS
- Dendritic cells in the skin phagocytose microbes that enter the skin and present the antigens to T cells.
Macrophages are APCS. - After digesting an organism, they transport the antigenic fragments to their own cell membrane and display it on their surface (see picture on next slide).
- They present the antigen to the correct T cell
Abnormal cells can also be APCs. - The abnormal proteins they display mark the cells for destruction.
T CELLS
- activated T cells divided 4 types of speclaised cells produced
CYTOXIC T CELLS: inactive cells carrying antigens by releasing toxins
- destroy abnormal body cells infected and cancer cells
HELPER T CELLS are essential for cell-mediated and antibody-mediated immunity.
They produce cytokines (e.g. interleukins and interferons, which support and promote cytotoxic T cells and macrophages.
They stimulate B cells to produce antibodies
REGULATORY T cells Turn off activated T and B cells and help to prevent the development of autoimmunity and protect the foetus in pregnancy.
MEMORY T Cells respond rapidly to another encounter with the same antigen.
ANTIBODY-MEDIATED IMMUNITY
- B cells mostly in lymphoid tissue (e.g. spleen and lymph nodes).
- B cells recognise antigens directly.
Activated B cells transform into plasma cells, which make antibodies. - B cells displays their antibodies on their cell membrane.
- The bound antibodies are antigen receptors
- B cells (with the help of T helper cells) enlarge and start to divide
Plasma and memory B cells are produced.
PLASMA CELLS AND ANTIBODIES
- Plasma cells secrete antibodies (Ig) into the blood.
- They also go into the tissues and body fluids.
- Antibodies bind to antigens so they are targets for cytotoxic T cells and macrophages.
- They bind to and neutralise bacterial toxins they activate complement.
ANTIBODY TYPES
IgA found in body secretions – breast milk, saliva. Prevents antigens crossing epithelial membranes and invading deeper tissues.
IgE on cell membranes of basophils and mast cells. Often found in excess in those with allergies
IgG attacks many different pathogens and crosses the placenta to protect the foetus
IgM produced in large quantities in the primary immune response. It is a potent activator of complement.
MEMORY B CELLS
- They remain in the body long after the initial episode of infection has been dealt with.
- The rapidly respond to the another encounter with the same antigen by stimulating production of antibody-secreting plasma cells
ACQIURED IMMUNITY - PRIMARY RESPOSNES
Primary response is to an antigen for the first time.
Antibodies take longer to respond because of the time needed to activate T cells, which then stimulate B cell division.
If the immune system has responded effectively, there will be a population of long-lived memory B cells
ACQUIRED IMMUNITY - SECONDARY RESPONSE
immune response is a lot faster and more powerful due to rapidly dividing memory T and B cells.
The pool of memory cells is increased (as in booster vaccinations)
The main antibody is IgG, which is more effective than IgM.
AGEING
- Immunity declines with advancing age
- thymus shrinks to 25% max size (at puberty)
- reduce the functions of NK cells (more cancer)
