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Inflammation and Wound Healing Exam 1 > Structure of B and T Lymphocyte Receptors > Flashcards

Structure of B and T Lymphocyte Receptors Flashcards

1
Q

what do B cell receptors contan?

A
  • an antibody of defined specificity
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2
Q

what do T cell receptors contain?

A
  • structure that resembles part of an antibody molecule (Fab fragement) that is specific for peptides from the antigen that was presented to the naive T lymphocyte by the APC
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3
Q

what is the structure of B-cell receptors?

A

quaternary protein with two identical heavy chains and two identical light chains

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4
Q

what are co-receptors and what are some examples?

A

BCRs cannot signal directly when they bind an antigen so to transmit activation signals into the cell they use co-receptors
- Igα and Igβ
- CD19/CD21/CD81

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5
Q

explain how lignand receptor binding causes molecular changes?

A

dimerization or multimerization occurs and the receptors are clustered and localized in lipid rafts

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6
Q

what are the two antibody forms?

A

membrane bound form and secreted Ig form

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7
Q

what produces antibodies?

A

B lymphocytes and plasma cells

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8
Q

what are plasma cells?

A

highly differentiated B lymphocytes that are specialized in the secretion of antibodies

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9
Q

what is the structure of the typical antibody molecule IgG?

A
  • divalent
  • two binding sites for cross linking
  • proline rich hinge region that allows an extension
  • 2 identical light and 2 identical heavy chains
  • held together by disulfide bonds
  • contains variable and constant domains
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10
Q

what are the two light chains and what are the five heavy chains?

A
  • kappa and lambda
  • mu, alpha, gamma, delta and epsilon
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11
Q

compare the amino acid sequences for the variable region and the constant region?

A
  • variable region: the amino acid sequences of the
    antibody molecules produced by different clones of B
    lymphocytes VARY
  • constant region: identical amino acid sequence even
    when different clones of B lymphocytes produce antibody molecules.
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12
Q

what is the difference between the C terminal and N terminal of a typical antibody molecules (IgG)?

A
  • N terminal: antigen binding site/recognition site (Fab)
  • C terminal: mediates effector activities (Fc, c=crystallization)
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13
Q

what is a paratope?

A

the structure of the Fab fragment of an ANTIBODY that makes direct contact with an antigen

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14
Q

what is an epitope?

A

the portion of the ANTIGEN that is bound to the antibody

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15
Q

how many hypervariable regions are there in the heavy and light chains of an antibody?

A

3 on each

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16
Q

the residues in the hypervariable region make?? what is another name for the hypervariable region?

A
  • the closest contact with antigen at the antigen combing sites
  • complementary determining region
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17
Q

what does the amino acid sequence in the complementary determining regions determine?

A

shape, charge and chemistry of an antibody for its antigen ie specificity

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18
Q

describe antigen-antibody interactions

A
  • non-covalent bonds
  • reversible
  • require close steric fit
  • closer fit= tighter fit= higher affinity binding specificity
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19
Q

what is affinity?

A

the strength of an individual bond for a certain interaction between antibody and antigen

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20
Q

what is avidity?

A

combined strength of binding of multiple interactions (multivalent)

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21
Q

for T cell receptor complexes with coreceptors what is the functions of CD3, CD4 and 8 and CD28?

A
  • CD3 contains ITAMs that transmits signals to the cell
  • CD4 and CD8 increase the avidity
  • CD28 engages CD80/86 on the antigen presenting cell to activate the T cell
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22
Q

what are the 5 immunoglobulins?

A
  • IgG
  • IgA
  • IgM
  • IgD
  • IgE
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23
Q

what is the heavy chain and light chain composition of secreted IgG?

A

heavy chain: gamma
light chain: kappa or lambda

24
Q

what are some specific properties of secreted IgG?

A
  • monomer
  • crosses the placenta (protects fetus only in womb)
  • found in the blood stream and tissue fluid
25
Q
A
26
Q

what is the heavy chain and light chain composition of IgM?

A

heavy chain: mu
light chain: kappa or lambda
junction chain

27
Q

what are some specific properties of IgM?

A
  • pentamer
  • found in serum and intravascular spaces
  • H chain has extra CH4 domain
28
Q

where is the membrane form of IgM expressed and what does it do?

A
  • expressed on cell surface of early B cells as a monomer to serve as a B cell receptor
29
Q

what is the first immunoglobulin produced in infants and in an immune response?

A

IgM

30
Q

which antibody is the most efficient antibody for agglutination and complement fixation?

A

IgM

31
Q

what is the heavy chain and light chain composition of IgD?

A

heavy chain: delta
light chain: kappa or lambda

32
Q

what are some specific properties of IgD?

A
  • monomer
  • it is surface bound on mature B cells and not secreted
33
Q

which immunoglobulin is used as a signal receptor?

A

IgD

34
Q

which immunoglobulin triggers further differentiation of B lymphocytes?

A

IgD

35
Q

what is the heavy and light chain composition of IgA?

A

heavy chain: alpha
light chain: kappa or lambda
j chain
secretory side piece

36
Q

what are some specific properties of IgA?

A
  • dimer
  • found in external secretions
  • absorbed through the intestinal lumen
37
Q

what are the steps of IgA transport?

A
  1. IgA dimer binds to poly-Ig receptor on the internal surface
  2. IgA receptor transported across vesicles
  3. vesicle fuses with membrane on the external side
  4. cleave secretory piece to release IgA
38
Q

what are some specific properties of IgE?

A
  • monomer
  • H chains have extra CH4 domains in which they bind to IgE receptors on basophils and mast cells
  • lowest concentration compared to all other antibodies
39
Q

what is the heavy chain and light chain composition of IgE?

A

heavy chain: epsilon
light chain: kappa or lambda

40
Q

what are some specific activities of IgE?

A
  • protects against parasitic infections
  • associated with allergies or hypersensitivities
  • its a reaginic antibody (gives us allergies)
  • binds to IgE Fc receptors on basophils, eosinophils and mast cells causing degranulation
41
Q

what is a variable region?

A

the amino acid sequences of antibody molecules produced by different clones of B lymphocytes vary

42
Q

what is a constant region?

A

it has an identical amino acid sequence even when different clones of B lymphocytes produce antibody molecules

43
Q

what is the antigen independent phase ?

A

stem cells —-> pro B/T cells —-> immature B/T cells —-> mature B/T cells with BCR/TCR
- generates a vast repertoire of B/T cells with receptors of different specificity

44
Q

what are the mechanisms used by B cells to produce their vast repertoire?

A
  1. selection of many mini-gene segments
  2. recombination
  3. addition and deletion
  4. association of many different heavy and light chains to form binding sites
45
Q

what are mini genes?

A
  • recombination of gene segments to create different possible antigen binding sites
46
Q

what are the mini segments of mini genes?

A
  • variable (V)
  • diversity (D)
  • joining (J)
47
Q

what are the mini gene segments that make up light chains and heavy chains?

A
  • L chains: V + J
  • H chains: V + D + J
48
Q

what is the 12/23 rule?

A

recombination signal sequences that direct recombination have a nonamer and heptamer sequence separated by a 12 or 23 basepair spacer sequence where a 12 bp sequence MUST pair with a 23 bp sequence for the recombination to occur

49
Q

what joins the gene segments and how?

A

RAG1/2 recombinase encoded by the RAG gene recognizes and cuts DNA at the immunoglobulin coding region and the RSS

50
Q

where are the 3rd hypervariable regions located (CDR3)?

A

junction of V-J and D-J

51
Q

what is allelic exclusion?

A

is the process by which only one allele of a gene is expressed while the other allele is silenced.

52
Q

why is allelic exclusion important?

A
  • this mechanism ensures that a single B cell expresses one specific type of B cell receptor (BCR), or a single T cell expresses one specific type of T cell receptor (TCR). It prevents the production of receptors with mixed specificities, which would dilute the immune response and reduce its effectiveness.
53
Q

what are the different heavy chain assortments for TCR?

A
  • different beta chains and alpha chains pair for TCRab
  • different delta chains pair with gamma chains for TCRgd
54
Q

what are somatic hypermutations and when do they occur?

A
  • introduction of point mutations in the V region of rearranged H and L chains
  • occur on B cells after encountering antigen
55
Q

what can happen after a somatic hypermutation?

A

affinity maturation

Inflammation and Wound Healing Exam 1 (13 decks)

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