Summary FCH-21806 Immunological aspects

Summary Food Related Allergies and Intolerances FCH-21806 Period 2
Immunological aspects
Introduction into immunology
• Introduction of the immune system
- Despite being surrounded by harmful organisms  toxins and threat of our own cells turning
into tumour cells  humans manage to survive  due to our immune system
- Immune system made up of:  all work together to generate immune response that
protects us from MO, removing toxins and tumours
o Organs
o Tissues
o Cells
o Molecules
- Immune system can (within 10 days):
o Identify a threat
o Mount attack
o Eliminate pathogen
o Remember
- Immune system has prolonged reactions = chronic inflammation
- Self and non-self cells
o Key to healthy immune system is ability to distinguish
between body’s own cells (self) and foreign cells (non-
self)
o Body has cells that carry distinctive self-marker
molecules and when immune defenders encounters
cells/organisms  carrying markers that say foreign  attack
o Antigen: anything that can trigger this immune response
▪ Microbe, virus, part of microbe or tissues/cells from other persons
▪ The immune system can mistake self for non-self  launch attack against
body’s own cells/tissues  autoimmune disease
▪ When immune system respond to seemingly harmless foreign substance 
allergy  antigen is called allergen
• Functions of the immune system
- Total area for protection: 2m2 skin, 80m2 lung and 350m2 gut tissue
- Infection = non-self
o Immune system is protecting against infection  help to protect against diseases
- Tumour = modified-self
o Provoke danger from the inside  body cells can be modified due to exposure to UV,
toxic compounds, air  modified self-cells
o Immune system is protecting against tumours from the inside
- Immune system is organized in single cells, floating around in body  difficult system




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,• The innate immune system
- Cells that are non specific
- Can distinguish self and non self cells  but not
distinguish invaders from each other
- Feverishly fast response
o Within minutes to hours
o Causes fevers
- No memory associated
- Also includes:
o Chemical barriers
▪ Lysozymes in tears
▪ Low pH in stomach
o Physical barriers
▪ Epithelium in skin & gut
▪ Cilia in airways
- Cells: dendritic cells, NK, neutrophils, macrophages
- Molecules: acute phase proteins, anti-microbial substances, cytokines, chemokines,
complement enzymes
- Characteristics: rapid kinetics, omnipresence (present everywhere in body)
• The adaptive immune system
- Highly specific for each invader  can identify them by unique parts/antigens  can
distinguish between friendly and potential deadly ones
- Has to be primed/activated  differentiate into right cell
- Disadvantage: Takes a few weeks
- Advantage: Immunologic memory
- Cells that are activated in adaptive immune response
undergo clonal expansion  massively proliferate  each
time adaptive immune cells see same pathogen 
massively proliferate again  stronger and faster response
each time that pathogen comes around
- Once destroyed  most of colonially cells die off = called
clonal deletion
o Some survives as memory cells
- Cells: B- and T-lymphocytes, macrophages, dendritic cells
- Molecules: cytokines, antibody molecules
- Characteristics: specificity, amplification, memory




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,• The phases of immunity




• Difference innate and adaptive immune system  how they
recognize cells
- Adaptive: recognizes pathogen by specific antigen
- Innate: Pathogen Associated Molecular Patterns (PAMP)
o Include things like:
▪ Lipopolysaccharides (LPS)
▪ Lipoproteins
▪ Peptidoglycans
▪ Lipoteichoic acid (LTA)
o Found in pathogenic and non-pathogenic organisms
o Essential for survival of all pathogens  because of
PAMP pathogen can be eliminated by immune
response
o Innate immune cells have special receptors to identify PAMP  PRR (Pathogen
recognition receptors)  3 types:
▪ Intracellularly
➢ Pathogen inside the cell  cell will release cytokines or cell will die
➢ NOD-like receptors
▪ Extracellularly (on cell membrane)  2 options after binding PRR and PAMP:
➢ Engulf pathogen  release acidic lysosomal content into pathogen 
destroying pathogen
❖ Often with mannose and scavenger receptors
➢ Send signal to nucleus  to secrete cytokines or interferons
❖ Toll-like receptors (signalling receptor)
▪ Secreted PRR (by liver and immune cells)
➢ Complementary receptors  induce complement cascade
o All PRRs trigger innate immune response  obstinate pathogen  activate
complement protein  phagocytize pathogen  activate inflammatory mediators 
secrete cytokines, pro-inflammatory cytokines




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, o Big blue cell (macrophage) interacting with virus/bacterium/parasite on cell surface
of these organisms there are molecules (Pathogen Associated Molecular Patterns) 
essential to effect host cell  cannot afford to mutate (loose capacity to infect cells)
 immune system can recognize them by specific receptors (Pattern Recognition
Receptors) (able to recognize)
o TRL2 = recognizes gram positive bacteria  not specific, but the total group
o TRL4 = recognizes gram negative bacteria  not specific, but the total group




• Crucial role of dendritic cells
- Cell type that shows many extensions and is particularly present in those places where
antigens comes in (nose, lungs, skin, gut)
- First cells that take up antigen to activate immune response  immune system can respond
to these fragments of these organisms/virus/micro organisms
- Connects both systems: innate and adaptive




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