IMMUNOGLOBULINS

Question 1

IMMUNOGLOBULINS

Answer 1

The term of y-globulin and Ig are not synonymous. Ig is a functional term while y-globulin is a physical term
- glycoproteins,secreted by plasma cells
belonging to the B lymphocytes
-AKA antibody

Question 2

Structure of Immunoglobulin

Answer 2

consist of 2 identical heavy (H) and 2 identical light (L) chains.
* Combined through disulfide bridges.
* Is a Y-shaped tetramer.
* Both the H and L chains contain variable (V)
and constant (C)

Question 3

Papain

Answer 3

→ cleaves the Ig at the hinge region into
✓2 Fab (fraction antibody)
✓1 Fc (fraction crystallisation)

Question 4

Pepsin

Answer 4

→ cleaves the Ig at a site towards the carboxy terminal part into
✓Fab2
✓1 Fc

Question 5

Classes of Immunoglobulins

Answer 5

Depending on the heavy chain make up,
1. IgG → gamma (γ)
2. IgA→alpha (α)
3. IgM→Mu(μ)
4. IgE → Epsilon (ε)
5. IgD→Delta (δ)

Light chain of Ig can be either kappa (κ) or lambda (λ).

Question 6

IgG

Answer 6

• 2 H chains and 2 L chains – H chains is gamma type
• Is the major antibody; about 75-80% of total Ig in
  circulation.
• seen in secondary immune response.
• can cross placental barrier and protects the newborn child from infections. seen in neonatal circulation up to 2-4 months.

Question 7

IgM

Answer 7

-5 Y-shaped units held together by J-chain polypeptide – can combine with 5 antigens simultaneously,very effective for agglutinating bacteria.
* H chain of Mu(μ).
* large molecule-cannot come out of vascular space.
* predominant class of antibodies in primary response.
-Natural antibodies.Thus, a person having blood group A antigen will have anti-B antibodies in his circulation (isohemagglutinins).produced without any known antigenic stimulation, and hence called natural antibodies.
*cannot cross placenta, and therefore the fetus, even though it carries an incompatible antigen, is protected from natural antibodies of the mother.

Question 8

IgA

Answer 8

usually are dimers (double units) held together by J chain.
* H chain of alpha (α).
*Most abundant in body
secretions (saliva, tears, sweat, mother’s milk
and the walls of intestine).
* AKA secretory antibodies.

Question 9

IgE

Answer 9

-Lowest concentration in serum (0.004%) but increase in response to allergic and parasitic infections.
* H chain of Epsilon (ε).
* They mediate allergy, hypersensitivity and anaphylaxis.
-have property to fix on mast cells and
basophils, which release histamine and cause allergy.

Question 10

IgD

Answer 10

• single unit.
  *Present in low concentration (0.2%).
• H chain of Delta(δ).
• Present on the surface of B cells.
• Function is not known.

Question 11

multiple myeloma

Answer 11

abnormal plasma cells secrete excessive numbers of monoclonal light chains of Ig(no heavy chain) and excreted in the urine.

Question 12

Bence-Jones Proteins

Answer 12

*the monoclonal light chains (κ or λ) of Ig found in the urine.
* low molecular weight (20k – 40k) and excreted in urine which often damages the renal tubules.
*Testing to diagnose and monitor multiple myeloma.