intro to immuno Flashcards

1
Q

what problems arise when the immune system fails to recognize self and non-self?

A

no self recognition = autoimmunity

no non-self recognition = no protection against infection

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2
Q

characteristics of innate immunity (in contrast to adaptive)

A
  • present at birth (does not change with age)
  • rapid
  • relies on pattern recognition (common patterns of carbs/proteins on the surfaces of infectious organisms)
  • not specific
  • no memory
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3
Q

characteristics of adaptive immunity (in contrast to innate)

A
  • slow on first exposure
  • adapts to antigens
  • very specific (recognition at the amino acid or DNA sequence level)
  • memory
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4
Q

what cells/proteins are involved in humoral immunity?

A

B cells differentiate into plasma cells, which produce antibodies

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5
Q

what are the functions of humoral immunity?

A

targets extracellular immunity; antibodies…

  • neutralize toxins/viruses
  • opsonize bacteria
  • activate complement
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6
Q

what cells are involved in cell mediated immunity?

A

T cells: helper CD4+ and cytotoxic CD8+

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7
Q

what are the functions of cell mediated immunity?

A

targets intracellular pathogens:

  • directly kill virus infected cells
  • inhibit fungi, parasites, and intracellular bugs
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8
Q

B cell functions

A
  • differentiate into plasma cells => produce antibodies
  • differentiate into memory B cells
  • present peptides to T cells
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9
Q

T cell functions

A
  • CD4+ helper T cells: secrete molecules to activate B cells and CD8+ cytotoxic T cells
  • CD8+ cytotoxic T cells: directly kill cells
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10
Q

antigen vs immunogen

A

antigen = any substance capable of reacting with antibodies (proteins, small chemicals, polysaccharides)

immunogen = any substance that induces an immune response (proteins, but NOT chemicals or polysaccharides)

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11
Q

T cell dependent vs independent B cell response

A

Dependent = peptide antigens
- T cell recognizes a protein antigen => CD4+ T cell helps drive B cell response

Independent = non protein antigen

  • B cell response to multivalent non-proteins
  • IgM response
  • No T cells required; APCs and B cells in spleen involved
  • asplenic patients are more likely to have infection from encapsulated bugs
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12
Q

what is the function of MHC proteins?

A

present peptides on the cell surface to T cells

MHCI:

  • on all nucleated cells
  • recognized by CD8+ cytotoxic T cells
  • alpha chain and beta2 microglobulin

MHCII:

  • only on APCs (mΦ, dendritic cells, B cells)
  • recognized by CD4+ helper T cells
  • alpha and beta chains
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13
Q

how do T cell receptors and co-receptors interact to allow for antigen recognition?

A

TCR and co-receptor bind peptides presented by self MHC on the surface of other cells => can only recognize foreign peptides also in the context of a self MHC molecule

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14
Q

what are the two signals required for CD8+ T cell activation?

A
  1. Peptide recognition:
    - any cell presents a peptide antigen on MHCI
    - CTCR and CD8 co-receptor bind peptide
  2. Cytokine signalling
    - IL-2 secreted from CD4+ cells

=> CD8+ cells can kill via cytotoxin molecules

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15
Q

what two signals are required for CD4+ T cell activation?

A
  1. Peptide recognition
    - APC phagocytoses extracellular pathogen and presents peptide on cell surface MHC II
    - TCR and CD4 co-receptor bind peptide
  2. Cytokine signalling
    - APC B7 protein binds T cell CD28
    - cytokine production and immune response
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16
Q

passive immunity

A
  • transfer of pre-formed antibody from one person/animal to another
  • rapid and short lived
17
Q

active immunity

A
  • induction of an immune response

- slow but long lived (memory)

18
Q

how is the immune response different in the young and old?

A

< 6 week: maternal IgG and IgA

nursing infants: maternal IgA

< 2 years: can’t generate a T cell independent B cell response

older adults: decreased T cell independent B cell response