Term
| An individual can generate 10^8 different antibody specificity. How is the genome large enough for this level of information? |
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Definition
The genes present aren't big enough for that many possibilities.
Diversity instead results from differences in heavy and light chains, during joining of chains, somatic mutation, etc |
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Term
| On a Kappa Chain gene, how many segments are there before any processing? |
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Definition
| 3 light chain loci and 1 heavy chain loci |
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Term
What gene segments does a single expressed kappa chain contain?
How many possibilities can result from their combination?
How many possibilities are possible for these combinations? |
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Definition
Vk + Jk +Ck
40 x 5 x 1 = 200 possibilities |
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Term
| For the V, J, D, and C gene segments, what do each of these letters stand for? |
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Definition
V= variable
J= joining
D= diversity (only on heavy)
C= constant |
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Term
| On a Lamda Chain gene, how many segments are there before any processing? |
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Definition
| 3 light chain loci and 6 C1 exons representing each subtype |
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Term
What gene segments does a single expressed lamda chain contain?
How many possibilities can result from their combination? |
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Definition
Vl + Jl +Cl
30 x 4 x 1 = 120 possibilities |
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Term
| How many possible variable regions can result from light chain gene combinations? |
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Definition
| 320 (120 from lamda and 200 from kappa) |
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Term
Which chromosome are light chain genes on?
Which chromosome are heavy chain genes on? |
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Definition
Kappa- chromosome 2
Lamda- chromosome 22
Heavy chain- chromosome 14 |
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Term
What gene segments does a single expressed heavy chain contain?
How many possibilities can result from their combination? |
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Definition
Vh + Jh +Ch
65x 27 x 6 = 10,530 |
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Term
| How many possible idiotypes can result from heavy and light chain combination? |
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Definition
10,530 x 320 = more than 3 million (10^6) possible idiotypes
Other processes such as imprecise joining can increase diversity |
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Term
| List and describe the steps of V/(D)/J recombination |
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Definition
1. Regions of DNA between V and J sequeces are recognized by RAG (recombinase) enzymes
2. Two of the RAG complexes are brought together, forming a stem loop structure that excises out and is deleted
3. This creates another level of diversity when the two unlike DNA is brought together, TdT adds nucleotides to allow base pairing and exonucleases remove unpaired ones |
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Term
| Once VDJ recombinase has combined the gene segments in a B or T cell, is the idiotype permanent? |
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Definition
Essentially permanent.
An exception is for memory B cells which undergo somatic hypermutation, which leads to affinity maturation in order to recognize an antigen |
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Term
| Which gene segment determines an Ig secondary biological characteristics? |
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Definition
| CH
(A constant gene on the heavy chain) |
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Term
| List qualities of the B Stem Cell stage |
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Definition
-Develop under bursal equivalent
-Located in bone marrow and blood |
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Term
| List qualities of the Pro-B cell stage |
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Definition
-Most primitive recognizable stage
-Assembly of heavy chain
-Located in bone marrow and blood |
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Term
| List qualities of the Pre-B cell stage |
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Definition
-Heavy chain expressed
-Assembly of light chain (k or l)
-Located in periphery |
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Term
| For any given B cell, how many possible light chains could be chosen? |
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Definition
4 possible (1 kappa and 1 lamda from each parent)
1 chosen during Pre-B cell stage, other 3 silenced |
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Term
| List qualities of the Immature B cell stage |
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Definition
-Cell begins to express complete IgM
-Idiotype completely determined
-Responses negatively to self immunogens, for tolerance |
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Term
| List qualities of the Mature B cell stage |
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Definition
-Surface IgD and IgM expressed
-Surface molecules acquired |
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Term
| How many B cells are produced in the body per day? What happens if they are never stimulated by antigen? |
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Definition
About 10^9 made a day, but die in several weeks if not stimulated by antigen.
About 1 in 100,000 could react to any given epitope |
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Term
| How long do plasma cells life in the body? |
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Definition
About 4 days
But memory cells can reside in lymphoid tissue for years |
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Term
| Define isotype (class) switching |
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Definition
Upon antigen stimulation, memory cells provide antibody of the same specificity but different secondary activity
A similar process to VJ binding, irreversible splicing |
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Term
| Define somatic hypermutation |
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Definition
-Occurs in V/J and V/D/J exons during an immune response
-Results in antibodies of increased or decreased affinity
-Cells of higher affinity receptors are selected to "mature" the immune response |
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Term
| Describe the system to limit antibody synthesis once an effective immune response has been launched |
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Definition
| Antigen-antibody complexes bind to B cells via Fc receptors to suppress the B cells via negative feedback |
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Term
| What two events in B cell development are reversible? |
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Definition
1. Coexpression of IgM and IgD
2. Change of synthesizing secreted antibody instead of membrane Ig |
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Term
When do B cells first start being produced in an individual?
Where are they first seen? |
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Definition
B cells first appear in the fetal liver 8 weeks after conception
They are produced in the bone marrow during the second trimester |
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Term
| List the isotypes in the order that they appear in a fetus |
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Definition
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Term
| How and when does a fetus get immunity? |
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Definition
| Active transport of maternal IgG begins about the 16th week, but mostly after 34th week |
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Term
| What can indicate intrauterine infection? |
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Definition
Presence of IgM and IgA in the cord blood
(IgG is normal since it is transferred through barriers) |
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Term
| How long does a baby have maternal IgG? |
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Definition
Up to six months after birth
(Also, IgA is transmitted through breast milk) |
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Term
| When should routine pediatric immunizations be started? |
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Definition
| Within the first two months of life |
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Term
| When is a person's immune response reasonably mature? |
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Definition
| By 2-3 years of age, but inexperienced |
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Term
| When is serious congenital immunodeficiency usually detected? |
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Definition
At 3-6 months of age, after maternal immunity wanes
Often detected during a reaction to a live vaccine |
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Term
| How does puberty affect immunity? |
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Definition
1. New exposures due to new experiences
2. Thymus reaches maximum size |
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Term
| Describe the size of the thymus throughout life |
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Definition
Maximum size (~35g) during puberty then begins involution until a small mass (~6g) remains in later adulthood
But shriveled thymus works just as well |
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Term
| How many acute infections does a normal adult contract a year? |
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Definition
2-5 common infections
Usually determined by environmental factors |
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Term
| Does immunity decrease with age? |
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Definition
No, there's no evidence of this.
However, autoimmune and neoplastic diseases are correlated with age |
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Term
| What is the effector function of SIgA? |
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Definition
| To bind to organisms in external secretions and prevent their attachment to mucous membranes |
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Term
Define opsonin
Give an example |
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Definition
A substance that enhances phagocytosis
IgG, complement proteins via Fc receptors |
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Term
| Define toxin neutralization |
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Definition
| Physical binding of an antibody (usually IgG) to prevent a toxin binding to its receptor |
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Term
| Define virus neutralization |
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Definition
| Physical binding of an antibody (usually IgG) to prevent a virus binding to its cell receptor |
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