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Biomolecular Mechanics > immunoglobulins > Flashcards

immunoglobulins Flashcards

1
Q

what is another name for immunoglobulins

A

antibodies

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2
Q

what do antibodies do

A

they recognise antigens

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3
Q

what is an antigen

A

any substance which elicits an immune response

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4
Q

portion recognised =?

A

epitope or antigenic determinant

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5
Q

where are antibodies present

A

plasma, tissues, secretions and lymphatic system

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6
Q

what are the 5 classes of immunoglobulins

A

IgG
IgM
IgA
IgD
IgE

they provide recognition function and trigger effector functions

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7
Q

what bond holds immunoglobulins together

A

disulphide bridges

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8
Q

what is Fab

A

Fragment antigen binding - responsible for binding antigen

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9
Q

what is Fc

A

Fragment crystallisable - responsible for effector function

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10
Q

what are the two types of light chains

A

Lamba and kappa
all antibody classes use these same light chains

in any individual antibody molecule both light chains are the same

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11
Q

what determines the class of antibodies

A

heavy chains

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12
Q

light chains fold up into how many globular domains

A

2

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13
Q

heavy chains fold up into how many globular domains

A

4 or 5

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14
Q

what is each domain comprised of and what links them

A

they are comprised of 2 beta sheets and are linked by disulphide bridges to form a beta barrel

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15
Q

what do n-linked oligosaccharides attach to

A

Asn residue in the sequence Asn-X-Ser/Thr where x is an amino acid except Pro

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16
Q

what does CDR stand for

A

complementary determining region

17
Q

what happens when VH and VL domains are paired

A

their 6 CDRs lie close together and create the antigen-binding site

18
Q

what do antibodies recognize

A

structural epitope on the antigen

19
Q

antiboy binds antigens with various (blank) interactions

A

non-covalent

20
Q

Electrostatic forces

A

Attraction between opposite charges e.g.NH3+ and COO-

21
Q

Hydrogen bonds

A

Hydrogen shared between electronegative atoms (N, O)

22
Q

Van der Waals forces

A

Fluctuations in electron clouds around molecules oppositely polarise neighboring atoms

23
Q

Hydrophobic forces

A

Hydrophobic groups interact unfavourablywith water and tend to pack together toexclude water molecules. The attractionalso involves Van der Waals forces

24
Q

explain and describe IgG

A
  1. Most abundant Ig in plasma (10 mg/ml)
  2. Y shaped2 HC of 50 kDa mass, 2 LC of 25 kDa mass4 subclasses - IgG1, IgG2, IgG3, IgG4
  3. Very efficient at triggering complement and phagocytosis via Fc receptors
  4. Only Ig class to cross the placenta from mother to fetus - protects baby in first months of life
  5. Predominant antibody of 2o response
25
Q

explain and describe IgM

A
  1. Only in plasma and secretions - too large to enter tissues
  2. Pentamer - 5 Y-shaped units joined by Joining (J) chain and disulfide bridgesHeavy chain has 5 globular domains
  3. Very efficient at activating complement
  4. Ten binding sites for antigen - very good agglutinating particles e.g. viruses
  5. Predominant antibody of 1o response
26
Q

explain and describe IgA

A

Important serum Ig (2-3 mg/ml)
Major antibodies in seromucous secretions.g. saliva, milk, colostrum gut, tracheobronchial system genito-urinary system
Class of antibody first encountered by many invading bacteria and viruses
1. Two subclasses - IgA1, IgA2
2. Monomeric and dimeric forms
3. Serum IgA – monomeric90% IgA1, 10% IgA2
4. Secretory IgA - predominantly dimeric40% IgA1, 60% IgA2Additional polypeptide (secretory component SC)derived from receptor mediating export to secretions
5. SC protects in the harsh environments of secretions

27
Q

IgE function

A

Associated with an allergic response
Important for protection against parasitic infections

28
Q

IgD

A

Very low serum concentrations
Found on the surface of lymphocytes
Function unclear - may be involved in the control of antibody response
Recently implicated in mucosal immunity

29
Q

Neutralizing antibodies=

A

IgG and IgA are efficient at binding to soluble toxins preventing them from binding to cell surface receptors

30
Q

what do allergic individuals make

A

IgE responses to innocuous antigens (allergens)FcRI is cross-linked —> release of inflammatory mediators like histamine

31
Q

summary

A

Structure on antigen recognised by an antibody is termed the‘epitope’ or ‘antigenic determinant’

Antibodies fold into globular domains with distinctive 3D structure

Hypervariable regions (CDR) in variable domains govern antigenbinding

Three-dimensional complementarity of structures of antigen binding site and antigen lead to high specificity and affinity

Different Ig isotypes are expressed at different body sites and have different functions

Antibodies act as flexible adaptors, linking antigen recognition to elimination mechanisms

Key functions of antibodies are blocking, neutralization, complement activation and cell activation through Fc receptor

Biomolecular Mechanics (18 decks)

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