Immune system Flashcards
What is the name of the group of proteins on the plasma membrane of all somatic cells which identifies the cell as being part of that particular individual?
Major Histocompatibility Complex (MHC)
in humans this is called the HLA (human leucocyte antigen) system
What is the name of the component which sets off an immune response?
antigen
What happens in the first stage of the innate immune response (immediate: 0-4 hours)?
infection
recognition by non-specific molecules in body fluids
removal of infectious agent
What happens in the second stage of the innate immune response (early induced: 4-96 hours)?
infection
innate immune cells activated
Pathogen-Associated Molecular Patterns (PAMPs) recognised and immune cells activate inflammation
removal of infectious agent
What happens in the adaptive immune response (late response: >96 hours)?
infection antigen transported to lymphoid organs naive B and T cells recognise antigen immune cells multiply and become active removal of infectious agent
What are cytokines?
small proteins which act to pass signals between cells
cells involved in both immune responses secrete and respond to cytokines released throughout the body and act both locally and at a distance
How does the increased cytokine level, primarily from the macrophages, influence the liver?
stimulated to produce acute-phase proteins which raises the viscosity of the plasma
an increase in C-reactive protein (CRP) indicates infection:
normal CRP level is <10 mg/L
10-40 mg/L found in mild inflammation and viral infections
40-200 mg/L found in active inflammation and bacterial infections
>200 mg/L found in burns and severe bacterial infections
How does the increased cytokine level, primarily from the macrophages, influence the hypothalamus?
increases body temperature which inhibits replication of pathogens and indicates infection
shivering and sweating may occur in severe fever
How does the increased cytokine level, primarily from the macrophages, influence the heart?
a very severe acute-phase response is septic shock
cytokines increase production of nitric oxide (NO)
this reduces cardiac output and increases vasodilation which decreases blood pressure
What is innate (natural) immunity?
the first line of defence against pathogens
it reacts much quicker than the adaptive system
What are the three functional characteristics of innate (natural) immunity?
it reacts rapidly to pathogens
it responds the same way each time it meets pathogens
it starts again on each occasion that it meets a pathogen
What does innate (natural) immunity consist of?
physical and biochemical barriers of the skin and internal membranes
the inflammatory process
cells of the innate immune system: phagocytes, natural killer cells, mast cells, eosinophils
the complement system which is activated and destroys pathogens
interferons (proteins) which prevent viral replication
How does the skin protect the body from infection?
secretions from sweat and sebaceous glands contain antibacterial and antifungal chemicals and macrophages
How does the respiratory system protect the body from infection?
goblet cells secrete mucus which traps pathogens
cilia move mucus up to the pharynx where it is swallowed
How does the renal system protect the body from infection?
the flow of urine usually prevents pathogens being established
it is often only when renal stones or other blockage occurs or flow of urine is reduced that urinary infections occur
How does the gastrointestinal tract protect the body from infection?
the acid and proteolytic enzymes in the stomach rapidly kill most bacteria entering
some reach the colon and compete with non-pathogenic bacteria normally present
What are the two main phases of the inflammatory response?
vascular and cellular
What happens in the vascular phase?
arterioles and capillaries supplying the damaged area dilate which increases blood flow and causes redness and heat
the permeability of capillaries is increased due to inflammatory mediators from damaged cells and increased pressure caused by increased blood flow to the area
plasma proteins move into the tissues through widened gaps in the capillary walls which increases osmotic pressure in the tissues and draws fluid in
What happens in the cellular phase?
leucocytes are chemically attracted to the site of injury when macrophages release cytokines (e.g. interleukins)
phagocytes arrive at the site of injury and engulf pathogens and cell debris
What are six inflammatory mediators?
histamine, prostaglandins, leukotrienes, serotonin, bradykinin, interleukins
What is histamine?
powerful vasodilator released by mast cells and basophils
increases vessel permeability and contributes to pain by sensitising nerve endings
What are prostaglandins?
contribute to smooth muscle contraction and stimulate nociceptors
promote the inflammatory response
What are leukotrienes?
slow-acting vasoactive substances released by leucocytes
attract eosinophils
What is serotonin?
increases vascular permeability and promotes vasodilation
What is bradykinin?
stimulates unencapsulated sensory nerve endings and is the primary noxious stimulus
What are interleukins?
released from lymphocytes and macrophages
promote communication between B and T cells
What are phagocytes (neutrophils and macrophages)?
mobile leucocytes which engulf and destroy pathogens
they have special receptors called pattern recognition molecules which recognise patterns associated with different types of pathogens (e.g. some identify the double-stranded RNA found in many viruses at some stage in their life-cycle)
phagocytes then engulf the microbes by endocytosis into a vacuole into which enzymes are secreted which kill the microbes
