2013C10 Write brief notes on innate and acquired immunity.

List:

· Table of differences

· Innate system: physicochemical, humoral, cellular components

· Acquired system: humoral and cellular components

Table of differences:

	Innate	Acquired
Evolutionary age	Older	Newer
Role	First line	Second line
Activity	Always active	Normally silent
Speed	Very fast: mins-hours	Slow first time: 3-4 days Fast second time <1day
Potency	Low	High
Specificity	No	Yes
Memory	No	Yes
Second exposure	Same	Much better

Innate:

Physico-chemical	· Barriers (e.g. skin, blood-brain barrier) · Constant flow (e.g. urine) · Bactericidal secretions: gastric HCl, lysozyme in tears, fatty acids in sweat
Humoral	· -Complement cascade o Series of zymogens o Opsonisation for phagocytosis o Chemotaxis for WBCs o Direct lysis by MAC o Activates B cells · Inflammatory cytokines o Macrophages release cytokines TNFα, IL1, IL6, IFN o Local effects: vasodilatation, capillary leak o Immune effects: chemotaxis, WBC proliferation · Acute phase reactants: o e.g. CRP -> activates complement
Cellular	· NK cells: o Recognizes PAMP/DAMP on MHC1 o Phagocytosis + lysosomal killing of virus-infected cell · Monocyte/macrophage: o Recognizes PAMP/DAMP on MHC1 o Phagocytosis + lysosomal killing of virus-infected cell and bacteria o Cytokine release · Granulocyte o Neutrophil: phagocytosis of bacteria o Eosinophil: phagocytosis of parasites o Basophil (blood): defence against parasites, role in allergy o Mast cell (tissue): defence against parasites, role in allergy

Adaptive:

Humoral

· Antibodies o Draw structure. o IgA in secretions o IgD on WBC, function unknown o IgM in plasma, for early response, activates complement o IgG in plasma, for later response and memory o IgE for parasites, helminths · Inflammatory cytokines: o For co-activation of T and B cells

Cellular

· Antigen presenting cells: o Macrophages and dendritic cells o Internalises Ag, presents on MHC2, activates TH cell · T cells o TH: recognizes Ag on MHC2; secrete cytokines, activate TC cells, activate B cell -> plasma cell o TC: recognizes Ag on MHC1 of infected cell; phagocytoses o TM: small number, long-lived, specific, produced after activation o TReg: prevent inappropriate immune response · B cells o Activated by specific activated TH or by recognizing Ag directly o Plasma cell: secretes antibodies o Memory B cell: small number, long-lived, specific

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