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

Time to onset

Very fast: mins-hours

Slow first time: 3-4 days

Fast second time <1day

Activity

Always

Normally silent

Potency

Low

High

 

 

 

Specific

Yes

No

Memory

No

Yes

Efficacy on 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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