Download L18, Part 2: Immunune System, continued

12
B Cell Activation
Signal 1: Antigen in B
cell receptor
Signal 1: Antigen in MHC II
recognized by antigen receptor
Immune System
Lecture 18, Part 2
Winter 2014
Signal 2: Co stimulatory
molecules
from
dendritic cell
Fig.
43.18
Intracellular pathogens
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• How recognize?
• Constant region
• Variable region
• Who recognizes?
– T cells
– Cell-mediated immune
response
• How to
activate
cytotoxic T
cells?
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T Cells
• ~ 10 million different T cells/body
• Only binds to antigen fragments presented by
host cells
– MHC class I proteins –
intracellular
Cell-Mediated Response
Signal 2: cytokines from
Helper T cell
Fig. 43.9
• Cytotoxic T cells
• Helper T cells
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T cell Activation
• Dendritic cells presenting (viral) antigen in both
MHC I and MHC II
• Helper T cell activation
Signal 1: CD8 T cell
recognizes antigen in
MHC I on dendritic cell
Virus
Signal 2: cytokines from
Helper T cell
Fig. 43.16
Fig. 43.17
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Cell-Mediated Response
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Clonal Selection of T cells
• Perforin molecules
• Granzymes
• Cell fragments can be targeted by antibodies for
disposal
Fig. 43.20
Fig. 43.17
Primary & Secondary Immune Response
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Variation in T cell and B cell Receptors
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Constant region
Variable region
Fig. 43.15
Fig. 43.11
Variation in T cell and B cell Receptors
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• How do we get the huge variability in receptors?
• Variety of
combinations
Fig. 43.13
– Variable /
Joining /
Constant
(light chain)
• Recombinase
• Recombination
permanent for
that B or T cell
Fig. 43.9
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Self vs. non-self
• As lymphocytes mature, tested for self
reactivity
• T cells migrate to & mature in thymus
• B cells mature in bone marrow
• Destruction of self-reactive cells
2
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Adaptive Immunity: Summary
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Plasma cells (B cells)
Adaptive immunity
• What cellular
changes need
to occur?
– Recognition of traits specific to particular pathogens
• Vertebrates only
• Mediated by lymphocytes
– B cells & T cells
• Specificity
• Memory
• Self/non-self recognition
Fig. 43.21
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Active & Passive Immunity
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Immunoglobin (Ig)
• Active Immunity
– Formation of clones of memory cells
• Passive Immunity
– Transfer of antibodies from mother to child
through the placenta or breast milk
• Short lived (weeks to few months)
• Immunization (vaccination)
– Artificial inducement of active immunity
– Introduction of antigens
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• How can pathogens evade detection by
the immune system?
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