Immunology

defence against disease

• usually microorganisms
• for them, the body is their ideal house
• adult gut -> 500 microbal species - COMMENSAL ORGANISMS
• we have eveolved with these and we need them as they protect against infection

1. competion for space
2. production of anti-bacterials -COLICIN

• antibiotics are bad because they destroy our commensals

PATHOGENS

• BACTERIAL 
• VIRUSES
• FUNGI
• PARASITES

we have a multilayer defebce system, this is made up of mechanical, chemical and microbiological barriers

if these barriers are breached 

• INNATE IMMUNITY comes into play
• the innate immune system 

1. reacts quickly 
2. recognises pathogen 
3. destroys the invaders
4. induces the INFLAMMATORY RESPONSE
5. informs ADAPTIVE IMMUNITY

pathogens are recognised and destroyed

1. bacterial cell surface induces cleavage and activation of complement
2. one complement fragment covalently bond to the bacterium, the other attracts an effector cell
3. the complement receptor on the effector cell binds to the complememnt fragment on the bacterium
4. the effector cell engulfs the bacterium, kills it and breaks it down

inflammatory response

1. healthy skin is not inflammed
2. surface wound induces bacteria, which activate resident effector cells to secrete cytokines
3. vasodilation and increased vascular permeability allow fluid, protein, and inflammatory cells to leave blood and enter tissue
4. the infected tisusue becomes inflammed, causing redness, heat, swelling and pain

adaptive immunity

• innate immunity can LIMIT infection but it needs some help to REDUCE infection 
• adaptive immunity is 

1. provided by lymphocytes
2. adapts to pathogens
3. long lasting

effector mechanisms in adaptive immunity

• progenitor cells give rise to lymphocytes with different specifity
• detection of a foreign antigen by the specific lymphocytes - CLONAL SELECTION
• activation results in proliferation and differentiation to many effector cells specific for the infection - CLONAL EXPANSION
• infection termination

immproves well with age

• PRIMARY IMMUNE RESPONSE- first encounter with a pathogen 

1. longer lag time
2. less specific response

• SECONDARY IMMUNE RESPONSE - second and subsequent infections with the same pathogen 

1. faster response
2. more specific response
3. principle of vaccination

all immune sytem cells derive from haematopoeitic stem cells

• haematopoiesis id formation of blood cells- red and white
• white blood cells- leukyocytes- immune system cells
• haematopoeisis shifts during development - yolk sac, liver spleen, bone marrow
• haematopoiesis occurs throughout…