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MCD - Immunology > Principles of immune response > Flashcards

Principles of immune response Flashcards

1
Q

Functions of immune responses

A
  • Protection of host from pathogenic microorganisms
  • Distinguishing self from non-self
  • Distinguishing self from abnormal self (cancerous cells)
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2
Q

Principles of immune responses

A
  • Activation requires recognition of danger signals.
  • Encountering a pathogen causes formation of specific antibodies
  • This leads to faster, larger, more efficient clearance of pathogen during second exposure
  • Highly polymorphic (variable) genes
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3
Q

Consequences of failure of immune system

A

This is immunodeficiency, increased infection, increased risk of cancer

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4
Q

Definition of autoimmunity

A

Recognition of self cells as harmful material by immune system

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5
Q

Definition of allergy/hypersensitivity

A

Recognition of harmless non-self as harmful

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6
Q

Two immune system response INITIATION strategies

A

Strategy 1 - Pattern Recognition Receptors

Strategy 2 - Antigen-specific receptors on lymphocytes

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7
Q

Summary of pattern recognition receptor strategy

A
  • Common molecular patterns
  • Germline encoded
  • Recognise (PAMPs) pathogen associated molecular patterns and (DAMPs) damage associated molecular patterns
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8
Q

Summary of antigen-specific receptors on lymphocytes used as initiation strategy

A
  • Each antigen receptor binds a specific site (epitope) on an antigen
  • Randomly generated through gene recombination in lymphocytes
  • Millions of potential different receptors possibly encoded
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9
Q

Definition of lymphocyte

A

Type of white blood cell which carries an individual receptor specific to a particular antigen

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10
Q

Antigen definition

A

A molecule that is recognised and bound by lymphocytes

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11
Q

Antibody definition

A

A soluble receptor specific to an antigen synthesised and secreted by B lymphocytes = Immunoglobulin (Ig)

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12
Q

Features of innate immunity

A
  • Fast
  • Germline encoded, pre-formed components
  • Limited specificity to DAMPs/PAMPs
  • Independent of previous exposure
  • No memory
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13
Q

What do DAMP and PAMP stand for

A
  • Damage Associated Molecular Pattern

- Pathogen Associated Molecular Pattern

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14
Q

Cells of innate immunity

A 
Macrophages/monocytes
Neutrophils
Basophils
Eosinophils
Complement
Natural Killer cells
Dendritic cells
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15
Q

Roles of innate immunity

A
  • Destruction of invading nucleic acids (viruses) in cytoplasm
  • Activation of inflammatory pathways and production of antiviral type 1 interferons
  • Contain and limit pathogenic spread whist adaptive immune response begins
  • Prime and direct appropriate adaptive response
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16
Q

Features of adaptive immunity

A
  • Slow
  • Clonal selection of randomly generated antigen receptors
  • Unlimited specificity, can theoretically bind any epitope with high specificity
  • Dependent on previous exposures
  • Memory (acquired immunity)
17
Q

Cells of adaptive immunity

A

B-lymphocytes

T-lymphocytes

18
Q

Roles of adaptive immunity

A
  • Selection and expansion of antigen specific clones
  • Targeted elimination of pathogen
  • Production of memory cells
19
Q

Antigen receptors of B and T cells

A

B cells - Membrane-bound Immunoglobulin

T cells - T cell receptor

20
Q

Process of clonal expansion

A
  • B/T lymphocytes circulate in naive, inactive form
  • Encounter complementary antigen, survive and proliferate
  • Produces clones of cells which present the same antigen
21
Q

Process of clearing infection

A
  • Cytotoxic T cells kill infected cells
  • Antibodies activate complement
  • Antibodies inactivate toxins directly
  • Antibodies activate Natural Killer cells
22
Q

Final fates of clonal lymphoctes

A
  • Death by apoptosis

- Survival as memory cells

23
Q

Cytokine definition

A

A substance which is secreted by certain cells of the immune system and have an effect on other cells

24
Q

Examples of cytokines and their actions

A
  • Interleukins, between WBCs
  • Interferons, anti-viral effects
  • Chemokines, chemotaxis and movement
  • Growth factors, growth and repair
  • Cytotoxic, tumour necrosis factor
25
Q

Process of cytokine release

A
  • Cytokine-producing cell stimulated
  • Cytokines released
  • Bind to receptor on target cell
  • Signal amplified inside target cell
  • Gene activation occurs
  • Leads to desired biological effects
26
Q

Three mechanisms of cytokine action

A

Autocrine - act on releasing cell
Paracrine - Act on nearby cell
Endocrine - Act on distant cell, travel by circulation

27
Q

Process of dendritic cell cytokine release

A
  • Network of cells located at likely sites of infection
  • Recognise microbial patterns, secrete cytokines
  • Capture pathogens and migrate to lymph nodes
  • Present antigens to adaptive immune system
28
Q

Definition of complement

A

A system consisting of a number of small proteins found in the blood, synthesised in the liver, which circulate as inactive pro-proteins

29
Q

Process of complement action

A
  • Stimulation by trigger
  • Proteases cleave specific proteins to release cytokines
  • Initiates further cascade of further cleavages
  • Stimulate phagocyte movement
  • Initiate inflammation
  • Construction of membrane attack complex
30
Q

Complement activation pathways

A

Classical pathway - activated by antigen-antibody complex
Alternative pathway - activated by pathogen surfaces
Lectin pathway - Antibody-independent activation of classical pathway, lectins bind to carbohydrates found on pathogens

31
Q

Mechanisms of control of complement

A
  • Short half-life of components
  • Dilution of components in biological fluids
  • Specific regulatory proteins
32
Q

Functions of complement

A
  • Lysis
  • Opsonisation
  • Activation of inflammatory response
  • Chemotaxis
33
Q

Features of acute-phase response

A

Fever
Increased WBC production
“Acute-phase” protein production in liver

34
Q

Acute phase proteins

A

C-reactive protein - activates complement
Mannan-binding lectin - activates complement
Complement
Fibrinogen - clotting

35
Q

Role of toll-like receptors

A

Involved in immune response as a type of pattern recognition receptor

36
Q

Mechanism of toll-like receptors

A
  • Ligands bind and activate receptor
  • TLRs recruit proteins in cytosol of immune cell with propagate signal transduction pathway
  • Upregulation or suppression of inflammatory response genes
  • Bacterial ligand = pathogen phagocytosed, digested, antigens presented to CD4+ T cells
  • Viral ligand = infected cell enters apoptosis or release interferons

MCD - Immunology (5 decks)

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