Question

a.Describe the structure of immunoglobulin

b. What are the functions of FAb and Fc potions?

c. Describe four or five ways that antibodies function in immunity

d. Describe the attachment of Abs to Ags.

Answer 1

a.Describe the structure of immunoglobulin

• Immunoglobulin is heterodimeric with four polypeptide chains
• It shows two light and two heavy chains.
• Disulphide bonds join the heavy chains with light chains.
• The two heavy chains also show linkage with disulphide bonds.
• Hinge region of the heavy chains is the region where the antibody of the heavy chains attaches to the disulphide bond.
• Constant region of the heavy chain determines the cellular toxicity of antigen, effector function of the antibody etc.

b. What are the functions of FAb and Fc potions?

• Fc is the portion of the heavy chain which is formed due to papain enzyme digestion of the two heavy chains forming CH2 and CH3 domains.
• FAB is the divalent fragment of the two heavy chains formed after papain digestion which possess two antigen binding sites.

c. Describe four or five ways that antibodies function in immunity

• IgG.......gets passed on from mother to fetus through placental crossing, gives passive immunity to fetus.
• IgM......First antibody made by the B cells, is also expressed on B cell surface.
• IgA......is a secretory immunoglobulin present in tears, saliva, mucous and it provides local immunity.
• IgD....is the antibody present on the B cells surface where it binds antigen.
• IgE....involved in allery.

d. Describe the attachment of Abs to Ags.

• The Abs -Ags complex shows the attachment of an antigen to an immunoglobulin.
• Abs are mostly present on the surface of the virions and they are released as viral products into the infected cells.
• Ab-Ag complex act as complement activation or as opsonization of antigens for phagocytosis.