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1
Q

Antibody

A

Antibodies are globulin protein of animal origin which are produced in response to antigenic stimulation with which it binds specifically.
If they release il 2 they act on cytotoxic t cells
If they release il 4 or 5 they act on b cells

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2
Q

Immunoglobulin

A

They are structurally similar protein of animal origin which are provided with antibody activity or no antibody activity

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3
Q

Diff btw antibody and ig

A

Antibody always bind to antigen and has biologicak functions
Whereas ig does not always vind to antigen and has biological functions

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4
Q

Ig having no antibody activity

A

Bence jones protein in mm

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5
Q

All antibodies are ig but all ig are not ab

A

1.Ab are located in gamma globulin fraction and because tehy immunologically react to antigen they are called immunoglobulins.

  1. Antibodies and ig are glycoproteins
  2. Apart from antibody globulins , the immunoglobulin class also contains cryoglobulin, macroglobulin and abnormal myelomal proteins
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6
Q
A
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7
Q

Properties of ig

A
  1. Synthesized by plasma cells
  2. Constitute 25-30% of total serum protein
  3. Chemically they are glycoproteins composed of 82-96% protein and 4-18% carb
  4. Present in serum, tissue and mucosal surfaces
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8
Q

Structure of ab

A
  1. They have a Y shape
  2. Contains atleast one basic unit or monomer
  3. Consists of 2 ends.
    a. An amino terminal end
    b. A carboxyl terminal end
    Consists of 4 polypeptide chains
    2 identical heavy chains
    2 identical light chains
  4. The chains are connected together by disulfide bond
  5. Light chain have a molecular wt of 25000 D and heavy chain have a molecular wt of 55000 D
  6. L and H chain are subdivided into variable and constant region.
  7. The regions are composed of 3 dimensionally folded repeated segment called domains
  8. Each domain is approx 110 AA long
  9. Within the variable region, there are some zones that show relatively higher variability in AA sequences. This zone is the hypervariable region or complementarity determining region (cdr)
  10. Forms the antigen binding site.
  11. There are 3 such zones in L chain and 4 in H chain
  12. As a whole 3/4th of h chain and 1/2 of l chain is constant region
  13. 1/4 of h chain and 1/2 of l chain is variable region
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9
Q

Length of constant region

A

104 aa for l chain
330 aa for gamma alpha and delta heavy chains
440 aa for meu and ebslong heavy chain

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10
Q

How many variable and constant regions

A

heavy chains are distinct in 5 igs
Ig gamma alpha delta . 3
Ie. Ch1 ch2 ch3
In meu and ebslong 4
Ch1 ch2 ch3 ch4

Light chain 1 variable domain Vl and one constant domain Cl

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11
Q

L chains are one of the two types. On the basis of Cl region of aa sequence

A

Kappa
Lambda

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12
Q

Extra

A

Variable region of both L and H chains have fab ie fragment antigen binding which is the antigen binding site

Constant region of heavy chain has fc portion ie. Fragment crystallizable and is responsible for biological or functional properties

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13
Q

Hinge region/joint

A

If immunoglobulin is treated with proteolytic enzyme papain then the ig will be dislodged at the hinge joint

The hinge region is rich in proline and cystein
2.It is quite flexible allowing the ig molecule to assume different positions thus helping the antibody to reach the antigen
3. Hinge region is sensitive to various enzymatic digestion.

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14
Q

General functions of ab

A

Primary func: ag binding
Sec func :
transplacental passage
Complement activation
Opsonization

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15
Q

Effector functions of antibody

A
  1. Opsonize the bacteria with or without complement
  2. Fixation of complement
  3. Agglutination of particles which includes bacteria and virus
  4. Neutralization of toxins released by bacteria
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16
Q

Classify immunoglobulin acc to name of heavy chain

A

IgG gamma chain
IgA alpha
IgM meu chain
IgE ebslong
IgD delta chain

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17
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A
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18
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A
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19
Q

IgM

A

1.Have meu chain as heavy chain
2.Present in two molecular forms
Monomeric
Pentameric
As a monomer it is present on surface of b cell
As a pentamer it is present in serum and composed of 5 basic units and one molecule of J chain. Joining chain to form a complete igM pentamer
3. Highest molecular wt
Monomer: 180000 D
Pentamer :900000 D
4. Present only in intravascular compartment not in body fluid or secretions
5. Have 10 antigen binding sites
6. Serum conc: 10% of total serum ig
7. Serum half life : 5 days

20
Q

Func of igM

A
  1. Main ig produced in pr response
    2.most potent ig in agglutination as it has 10 ag binding sites.
  2. First ig product in neonates
  3. Monomeric ig is present on b cell surface and is specific receptor for antigen
  4. Efficient in complement activation, ag IgM complex activates complement by classical pathway
  5. Neutralize bacterial toxins and viruses
  6. It is imp in ag ab reaction like agglutination test, cft
21
Q

IgG

A

Have gamma chain as heavy chain.
Consists of one basic unit or monomer
Molecular wt 15000 D
Serum conc 80% of total ogs in the body
Longest half life 23 days
Have 4 subclasses IgG 1 2 3 and 4
Complement fixation IgG3> IgG1> IgG2
All ig can cross placenta except igG2
Ig can cross placenta becoz receptor fcR1 (neonatal fc receptor) is present in synchiotrophoblast
2 ag binding sites
Receptor present in fc portion of igG

22
Q

Function of igG

A

1.predominant ab in sec immune response
2.only ab that can cross placenta though igG2 has poor ability
3.causes opsonization and enhances phagocytosis
4. Fixes complement which enhances bacterial killing
5.neutralizes bacterial toxins and viruses
6. Most effective against extracellular microorganisms
7. Raised after recovery period of chronic infection

23
Q

IgE properties

A
  1. Has ebslon chain of heavy chain
  2. Serum conc. Is 0.04 of total Ig
  3. Serum half life 2 days
    2 ag binding sites
    Molecular wt is 190000
    Minimum daily production
    Only heat labile ab inactivated at 56°C in 1 hr
    Has affinity for surface of mast cells
24
Q

IgE func

A

1.Mediates immediate hypersensitivity reactions
2. It participates in host defence against certain parasites
3. Protective against helminth infection
4. Fc region of IgE binds to surface of mast cells and basophils in type 1 hypersensitivity
5. Involved in allergic disorders

25
IgD
It has no known antibody activity It acts as an ag receptor on surface of many b cells Presence of it indicates more mature b cell
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IgA
Have alpha chain of heavy chain Present in secretory form and circulatory form(SERUM IGA) As a secretory ig it is present in saliva ,tears ,resp ,intestinal, and genital tract secretions ,in mothers milk and colostrum Serum IGA ... IGA1 AND IGA2 secretory iga has dimeric form which is 2 monomeric units joined by j chain. There is another joining segment called secretory component Secretory igA is derived from poly ig receptor present on the basolateral surface of epithelial cells.
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Function of igA
Local or mucosal immunity Effective against bacteria like Salmonella Niseria vibrio virus like polio influenza Breast milk is rich in igA and provides good protection to immunologically immature infant gut
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J chain
Joining chain MW 15000 Secretory form of igM and igA usually exists as polymers Synthesized by plasma cells
31
Secretory component
It is a glycoprotein MW 70000 Associated with igA secretion Synthesized by mycosal epithelial cells that make igA cross placenta
32
Enzymatic digestion of ig
Papain breaks peptide of hinge region Pepsin ficin
33
Antigenic Determinants of ig
Isotypes Allotypes Idiotypes
34
Isotypes
Vary from each other in AA Sequences of constant region of their heavy chains. Such constant region determinants are called isotype. They are present in all members of a species Eg. 5 classes if ig and their subclasses are isotypes
35
Allotypes
Additional antigenic features of ig that vary among the indivisuals due to genetic differences. They vary because the genes that code for L and H chains are polymorphic and indivisuals can have different alleles. Minor change in AA allotype markers are present on the constant regions of light and heavy chains They are present in some but not all mrmbers of a species Allotype markers are absent on meu delta and epslon heavy chains and lambda light chain
36
Idiotypes
Unique amino acids sequences present in paratope region of one member of a species act as ag binding site and also antigenic determinant to other members of same species. Each indivisual antigenic determinant of variable region is reffered to as idiotype Each ab will present multiple idiotypes. Idiotypes in an indivisual arises from continuous mutations in the genes of variable region
37
Immunoglobulin superfamily
Large no of membrane protein have been shown to possess one or more regions homologous to an immunoglobulin domain Each of these memb proteins are classified as a member of ig superfamily Ig heterodimer Poly ig receptor T cell receptor T cell accessory protein inc cd2 cd4 cd8 Cd28 Chains of cd3 Class 1 and 2 mhc molecules
38
Monoclonal ab and use
Ab derived from a single clone of plasma cell all having the same antigen specificity ie produced against a specific epitope of antigen Use 1. Identification of cells and clones:th and tc cells are identified by anti cd4 and anti cd8 ab 2. In home testing kits likr pregnancy test 3. To type tissue and blood for transplant 4. Treating diseases like cancer, organ transplant rejection, inflammatory disorders, Allergies and autoimmune disorders
39
Polyclonal abs
In response to whole organism or complex antigen, several different clones of b cells are activated. There is production of polyclonal abs by various different clones of plasma cells. These polyclonal abs react with a different antigenic epitope of complex ag.
40
Class switching
Early in immune response igM is predominant ab secreted by b cells But as maturation progresses same b cells undergo a phenomenon called class switching If tfh recognize ag peptide presented by b cells class 2 mhc molecule.. the tfh cell sends signal bacj to b cell Cd40 L binds to cd40B cell and Tfh produce IL 2 T cell induces AID (activation induced cytidine deaminase) and break double stranded dna in heavy chain locus. This removes meu and delta chain and brings vdj region to one of the c region. After rna splicing b cells begin to express igG ige iga instead of igm.
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Class switching depends on interplay of
3 elements 1. Switch region 2. Switch recombinase 3. Cytokine signals that dictate the isotype to which the b cell switches
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Antibody (1 decks)

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