Adaptive Immunity Flashcards by Joshua Parker

Name the 2 secondary lymphoid organs

Lymph nodes

MALTs (mucosa associated lymphoid tissue)

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What are the primary lymphoid nodes?

Bone marrow
Thymus
Spleen

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What is the molecular structure of antibodies? (3)

Glycoproteins
2 light chains
2 heavy chains

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What characterises a FAB fragment?

Vary in structure and antigen binding properties

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What characterises a FC fragment? (3)

No antigen binding activity
Can bind to phagocytic cells
Can activate the compliment

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What do B cell receptors induce? (5)

Signalling cascade:
Enhanced survival
Proliferation
Differentiation
Antibody secretion

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What are the 3 regions of T cell receptors and what is the purpose? (4)

Variable
Constant
Membrane anchoring
Recognises only MHC class molecules

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What is immunoglobulin repertoire?

Total number of antibody specificities a individual can create
~100 billion

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What is the benefits of adaptive immunity?

Immunological memory, faster response

Clonal selection

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What are the 4 sources of BCR (B cell receptors) variation?

Combinatorial V-D-J joining
Junctional diversity (addition or deletion of bases)
Somatic hypermutation
Variable combinations of H and L chains

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How many recombinant variations does V-D-J recombination provide alone?

~2m

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What is a V-D-J recombination?

A change in the DNA sequence of a immature B cells

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What is needed to cause a change in the L chain of a immunoglobulin?

A recombination that combines a random V and a random J segment

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What 2 changes is needed to cause a H chain variation?

1 random D and 1 random J

1random V segment and the combined DJ segment

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When does somatic hypermutation occur?

Occurs in rapidly proliferating B lymphocytes

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What are the 5 antibody classes?

Monomer
Dimers
Pentamers

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What antibody class are IgG, IgD and IgE antibodies?

Monomers

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What antibody class are IgM antibodies?

Pentamers

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What antibody class are IgA antibodies?

Monomers or dimers

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What does Ig stand for? (Eg. IgA)

Immunoglobulin

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What are the functions of Ig A,D and E

A: protects mucosal membranes
B: main B cell regulator
E: defends against parasites

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What are the functions of IgG and M?

G: neutralises viruses, activates compliment and helps ADCC
M: 1st antibody produced

What is an antigen?

A molecule reacts specifically with an antibody

What is the part of the antigen that is bound by the antibody?

Epitope

What are CD4 cells?

T helper cells

Where do T cells get created?

Bone marrow

Where do T cells mature?

Thymus

What do B cells do that T cells do not?

Secrete antibodies

What do Cd4 co receptors bind to?

MHC class II molecules

What do CD8 co receptors bind to?

MHC class II molecules

What is the order of chain restructuring?

H chain first then L chain

What does the enzyme activation induced cytidine deaminase do?

Causes a high rate of point mutations on the VDJ and VJ variable regions

What is the initial assembly of the H chain?

IgM | Contains 10 binding sites though limited effector mechanisms

What are the consequences of adaptive immunity?

Faster immunilogical memory Clonal selection makes t and B cells makes a better response Possibility of autoimmune disease

What is humoral immunity?

Antibody mediated immune response

What are the functions of the cell mediated adaptive immune response?

Cell mediated cytotoxicity via cytotoxic T cells (T cytotoxic) Activation of phagocytes via T helper Activation of B cells via T helper

What are the similarities between B and T cells?

Appearance Bone marrow origin Diverse Undergo clonal expansion after activation

What is CD8 T cells mechanism of action?

Recognise antigens on MHC I Activate Destroy via cytotoxicity

What is CD4 T cells mechanism of action?

Recognise antigens on MHC II activate Secrete molecules to activate CD8 and B cells

What is the mechanism of T cell activation (3)

Interaction and co stimulation Signalling cascade Proliferation and differentiation of T cells

What molecules do APC display?

MHC I and II molecules

What does the activation of T cells cause?

Causes expression of IL-2 and IL2 on the activated cell (autocrine function) Proliferates into effector cells (short lived)

What do the IL2 secretions cause?

Activation of macrophages Activation of T cytotoxic cells Activate B cells

What Is the role of of CD4 (T helper 2) cells

Control parasitic infections by: Activates eosinophils and mast cells Switches on B cells to produce IgE antibodies

What Is the role of of CD4 (T helper 17 and F) cells

T17: stimulate neutrophils Tf: stimulate B cells to produce antibodies

What are the 2 mechanisms of CD8 activation?

By mature dendritic cells | With help of CD4 cells

What is the mechanism of CD8 activation via dendritic cells?

MHC I activates IL2 receptors | Proliferation

What is the mechanism of CD8 activation via CD4 antibodies?

Cd4 secretes IL2 Increase in B7 molecules Activates CD8

What is the role of CD8 cells?

Kill infected target cells with viruses via apoptosis

What is the mechanism of action of fast independent cytotoxicity?

Recognition and attachment of NK cell to target Release perforin/granzymes into interstitial space (membrane attack) NK cell dissociation Target cell destruction by apoptosis

What is the mechanism of action of fas dependent cytotoxicity?

Proteolytic cascade in cytosol (caspases) Disruption in mitochondria Fragmentation of DNA

What is the purpose of the humoral immune response?

Protects against extracellular pathogens | Prevents spread of intracellular infections

How is the humoral response initiated?

Mainly via CD4 | Directly by bacterial antigens

What are the 5 main functions of antibodies?

Neutralisation of pathogens and toxins (not directly kill) Opsonisation of bacteria and viruses (phagocytic facilitation) Classic complement activation Activation of NK cells Degranulation of mast cells and basophils