Med Micro 6.2 - Specific Defense Part 1B (AB diversity) Flashcards

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1
Q

Why are live attenuated vaccines so wonderful?

A

They simulate the normal mode of entry etc of a pathogen

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2
Q

The class involved in the immune response depends on the type of foreign antigen, the portal of entry, and the antibody function needed. Why is this important?

A

Need to know to produce a good vaccine etc.

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3
Q

Antibody structure

A

Important parts: Fab (antigen binding), hyper variable sites (somatic mutation), Fc (biological activity mediation - has constant region and complement binding region)

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4
Q

Why is complement binding region important?

A

Needed to initiate the classical pathway of the complement system

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5
Q

Somatic mutations

A

Mutations that occur during our life time, not inheritable

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6
Q

B cell receptor (BCR)

A

AB in cytoplasmic membrane; multiple copies of a single type of BCR, all have same specificity determined by AB variable region; Antigen binding site is identical to that of the secreted antibody

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7
Q

How do we know that each different B-cell is unique genetically?

A

They all recognize a different epitope, so they must be.

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8
Q

Generation of AB diversity

A
  1. Multiple genes in the germ line DNA; 2. Variable recombination during the differentiation of germ line cells into B-cells; 3. Any light chain can combine with any heavy chain; 4. Mutation during the differentiation of germ line (naïve) B-cells into activated B-cells leading to increased affinity of antibodies during the immune response
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9
Q

AB diversity 1: Germ line DNA

A

Heavy Chain: 300 V, 10 D 4 J; Light: 300 V, 4 J; overall = 24 million; any one cell will only recombine in one of these possible ways resulting in 1 AB. (V = variable, D = diversity, J = junction)

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10
Q

RAG

A

Recombination activating gene. For heavy chain, randomly combines a D and J, then randomly combines a DJ to a V.

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11
Q

AB diversity 2: Variable recombination during differentiation of germ cells

A

Diversity can result is through a process of variable or “inaccurate” recombination. RAG involved here. Heavy chain: D + J, then DJ + V, then transcription and translation of polypeptide is completed. Light chain: V and J

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12
Q

AB diversity 3: Heavy and light combos

A

Any light chain can combine with any heavy chain

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13
Q

AB diversity 4: Somatic mutations

A

B cell clones that bind an antigen divide rapidly and come to dominate the antibody response to the antigen; The dividing B cell clones producing antibodies undergo affinity maturation for particular epitopes due to elevated mutation rates in their hypervariable regions, Those B cells with relatively higher binding affinities are stimulated to divide more rapidly (weak binding ones get apoptosis, not needed)

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14
Q

B cell activation and mutation: what’s the process?

A

(T helper dependent) T Helper activated by phagocyte, recognizes epitope on B cell and activates it to become plasma cell; Proliferates in follicle of lymph node, somatic hypermutations; B cells that bind to follicular dendritic cells exit, those that don’t apoptosis; AB secreting B cells and Memory B cells produced

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15
Q

How many possible ABs are there?

A

Result of RAG, deletions and insertions and mutations, 10^23 B cell receptor genes

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16
Q

Paratope details

A

AB binding site (about 50 aa), binds a specific epitope; about 15 of these contact a particular epitope, only about 5 dominate in binding - so one AB may bind different antigens

17
Q

Class Switching

A

All plasma cells begin by secreting IgM (Fc M region attached). Then they combine the variable region to another, generally IgG first, then possibly others after. The switch depends on mediators near site of infection.

18
Q

Isotype

A

Class of antibodies: G, M, A, D, E. These refer to the type of Fc region of the antibody.

19
Q

Allotype

A

Reflects genetic differences b/w members of the same species (can generate an immune response against them)

20
Q

Idiotype

A

Reflects antigen binding specificity of any particular AB

21
Q

If an O- person takes some A blood, will he automatically drop dead?

A

Need to generate antibodies, not there immediately,