Immune system Flashcards

1
Q

What are the two primary functions of the immune system?

A
  1. Immune response against pathogens

2. Recognition and elimination of transformed cells

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2
Q

How can the immune system be classified (into two main areas)?

A

Innate and adaptive

Within both innate and adaptive there is also cellular and humeral

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3
Q

Describe the innate immune system

A

Cellular; NK cells, neutrophils, dendritic cells, mast cells, eosinophils and macrophages

Humoral; complement, mannose binding lectin, LPD binding protein, CRP

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4
Q

Describe the adaptive immune system

A

Cellular; T cells, B cells

Humoral; antibodies

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5
Q

What are mechanisms of the innate immune system?

A

Phagocytosis
Complement (cascade)
Inflammation
NK cells

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6
Q

What are the stages of the adaptive immune response?

A
  • antigen recognition (APC)
  • lymphocyte activation (clonal expansion)
  • antigen elimination (humoral + cell mediated)
  • contraction (apoptosis)
  • memory (surviving memory cells)
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7
Q

Where are T cells produced?

A

Thymus

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8
Q

Describe MCH Class I

A

Part of T cell; recognised by CD8

Proteins made by our body degraded and presented

If cancer or virus this will change and they recognise these changes

T cells with MCH Class I are CYTOTOXIC

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9
Q

Describe MHC Class II

A

Part of T cell; recognised by CD4

Presentation of degraded bacterial antigens

These are the T Helper cells; present antigens and facilitate apoptosis

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10
Q

Where are B cells produced?

A

bone marrow

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11
Q

Describe B cell activation

A

Occurs in lymph nodes, requires T cells presenting an antigen

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12
Q

Which antibody is produced first in response to infection?

A

IgM

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13
Q

What antibody mediates the long-term response of the immune system to infection?

A

IgG

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14
Q

What does IgE mediate?

A

Allergies via mast cell activation

Also involved in fighting parasites

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15
Q

Where is IgA?

A

Mucosal surfaces

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16
Q

Which antibody is most prevalent?

A

Overall IgA, in blood IgG

17
Q

What are the functions of antibodies?

A
  • neutralisation of antigens
  • opsonisation of antigens; facilitates phagocytosis
  • activates complement system
18
Q

What are innate immune cells?

A

Mast cell
NKC
Basophil, neutrophil, eosinophil, monocyte
Mast cell, macrophage, dendritic cell

19
Q

What do dendritic cells do?

A

Present antigen via MHCII

Sentinel for immune system

Activates adaptive immune system

Internalises pathogen and processes it into peptides which it presents (antigens)

Naive T cells are activated

20
Q

Where do lymphocytes mature?

A

T cells; bone marrow then thymus

B cells; bone marrow

B and T cells then migrate to secondary lymphoid organs

21
Q

Describe cytokines and their functions

A
  • large and heterogeneous soluble proteins
  • communication system; locally or at distance
  • regulate and co-ordinate cells of innate and adaptive immunity
  • produced during normal haematopoeisis
  • produced in response to microbes, tissue damage or other antigens
  • produced by many cell types esp macrophages and T helper cells
22
Q

How do cytotoxic t cells kill cells?

A

Induce apoptosis in target cell

They induce the actions of phagocytic clearance

23
Q

Describe function of NK cells

A

Important against intracellular pathogens

May respond via their activating receptors to activating ligands on infected cells

Can kill infected cells

Produce IFN-g which will help stimulate macrophages, TH1 cells, CD8+ cytotoxic T cells

24
Q

How do NK cells induce apoptosis?

A

Release perforin which creates pore in membrane

Granzyme from NKC then enters cell and triggers apoptosis

25
How are antibodies bi-functional?
Fab portion (fragment antibody binding) binds to a specific antigen Fc portion interacts with different cells of immune system or complement
26
When are antibodies produced?
IgM produced as fetus IgG not until birth IgA not until 1-2months after birth Breast milk contains IgA
27
Describe antibody mediated immunity
First encounter pathogen; no antibodies while B cells differentiate into plasma cells. Then low vol IgM produced and small amounts IgG. Memory B cells also Encounter again; accelerated response, quick B cell proliferation to plasma cells - fast release specific IgG ABs and low vol IgM.
28
Describe immunologic tolerance
unresponsiveness to an antigen induced by previous exposure to that antigen
29
What are antigens that induce tolerance called?
tolerogens
30
What are some mechanisms of peripheral tolerance?
Anergy (functional unresponsiveness) Antigen recognition without co-stimulation T-reg suppression Deletion (cell death) Some self-antigens are sequestered from immune system by anatomic barriers
31
When does autoimmune disease occur?
When auto-reactive T cells or autoantibodies cause tissue damage through hypersensitivity reaction types II, III and IV
32
What is AIRE?
transcription factor expressed mainly by medullary epithelial cells in thymus "autoimmune regulator"