81⟩ What are haptens?
Haptens are small molecules that can react specifically with antibodies but cannot initiate immune response by themselves. They have property of antigenesity, but lack immunogenicity.
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200 Immunology Questions And Answers
82⟩ What is cell-mediated immune response?
It is based on T cells. These T cells are of two types.
T helper cells (TH)
T cytotoxic cells. (TC)
T helper cells interact with antigen MCH II present on APC (Antigen presenting cell) and secrete cytokines. These activate B cells, Tc cells and other phagocytic cells; these activated phagocytic cells kill microorganisms like protozoa and bacteria.
83⟩ What is humoral immune response?
It is based on antibodies. It is conferred to non-immune individuals by administration of serum antibodies from an immune individual. Antibodies bind to the antigens and facilitate their elimination by forming clusters through cross-linking.
84⟩ What is immunogenesity?
The ability of a material to induce an immune response is referred to as immunogenesity.
85⟩ Into how many types is immune response divided?
Immune response is divided into two types
1. Humoral immune response
2. Cell mediated immune response.
86⟩ What is an immunogen?
The ability of a material to induce immune responses referred as immunogenicity and such material is known as an immunogen.
87⟩ What is antigensity?
The ability of an antigen to combine specifically with the final products of immune response is called as antigensity.
88⟩ What is an antigen?
A substance that can produce a specific immune response when it is introduced into the animals and that can react specifically with the products of immune response is generally known as an antigen.
89⟩ What is opsonisation?
Immunoglobulins specific for particulate antigens such as bacteria play an important role by coating the surface of the bacteria and making the antigen more susceptible for phagocytosis. This process is called as opsonisation.
90⟩ What is Secondary IgA?
It is a dimer of molecular weight of 400,000 Daltons and sedimentation coefficient of 11S.
It contains a glycin rich polypeptide called a secretary component or secretary piece. It is relatively resistant to digestive enzymes and reducing enzymes. It is believed to play an important role in local immunity against respiratory and intestinal pathogens.
91⟩ What is serum IgA?
It is a monomer. It has a molecular weight of 160,000 Daltons and sedimentation coefficient of 7S.
92⟩ Give the classification of IgA.
IgA occurs in two forms.
* Serum IgA
* Secondary IgA
93⟩ Give the classification of IgG.
IgG is again sub divided in 4 sub classes. They are
1. IgG 1
2. IgG 2
3. IgG 3
4. IgG 4
94⟩ Briefly describe immunoglobulin M.
1) It constitutes 5.8% of total immunoglobulins. It has a normal serum level of 0.5 to 2 mg/ml.
2) it is a pentamer having a molecular weight of 900,000 Daltons and has a sedimentation coefficient of 19S. It is phylogenetically oldest immunoglobulin.
3) It has a half-life of about 5 days.
4) 5 monomers are arranged with their Fc fragments in the centre of the pentamer and the antigen binding sites towards the periphery of the molecule.
5) It is the first immunoglobulin to be synthesized by the foetus beginning by about 20 weeks of age.
6) It is 500-1000 times more effective than IgG in opsonization.
7) It particularly gives protection against microorganisms and other larger antigens that have repeating antigenic determines on their surface.
95⟩ Define immunoglobulin D
► Molecular weight of IgD is185, 000 Daltons and has a sedimentation coefficient of 7S.
► Its concentration in serum is about 3 mg/100ml, which constitutes about 0.2% of total Ig.
► It is mostly intra vascular in distribution.
► Its half-life is about 3days.
► It is rich in carbohydrates.
► IgD along with IgM occurs on the surface of unstimulated or mature B cells and serves as a reorganization receptor for antigens.
► No biological effect or function has been identified for IgD.
96⟩ Briefly describe immunoglobulin (Ig) E.
1) It is a monomer having a molecular weight of about 200,000 Daltons and has a sedimentation coefficient of 8S.
2) Its half life is about 2 days
3) Its concentration in serum is very low i.e. 0.3 mg/ml.
4) It exhibits unique property such as heat labiality and affinity for the surface of tissue cells such as mast cells.
5) It does not pass the placental barrier.
6) It is chiefly produced in the linings of respiratory and intestinal tracks.
7) It is responsible for the anaphylactic type of hypersensitivity.
8) The physiological role of IgE appears to be protection against pathogens by mast cells degranulation and release of inflammatory mediators.
9) Interleukin fold enhances the secretion of IgE.
97⟩ Briefly describe Immunoglobulin (Ig) A.
1) It is the second most abundant class containing 10-13% if serum immunoglobulins.
2) It has a half-life of 6-8 days.
3) IgA is actively secreted by mucosal associated lymphoidal tissue (MALT).
4) Its molecular weight is 60,000 Daltons.
5) IgA is synthesized locally by plasma cells and dimerized intra-cellular before secretion, with the help of cysteine rich polypeptide, called the J chain, which has a molecular weight of 15,000.IgA functions by inhibiting the adherence of coated microorganisms to the surface of mucosal cells.
98⟩ Briefly describe Immunoglobulin (Ig) G.
1) This is the major serum Ig containing 75% of the total serum immunoglobulin concentration.
2) It has a molecular weight of 150,000 Daltons and sedimentation coefficient is seven.
3) Its half-life is approximately 23 days.
4) It is the Ig, which is normally transported across the placenta and provides natural passive immunity to the newborn
5) It participates in immunological reactions such as compliment fixation, precipitation, and neutralization of toxins and viruses.
6) It is secreted in large amounts during secondary immune response.
99⟩ What are isotypes?
IgG, IgA, IgM, IgD, IgE classes are variants of immunoglobulin molecule. They are termed as isotypic variants or isotypes.
100⟩ How immunoglobulins are measured?
Immunoglobulins are measured using sedimentation coefficient (measured by Svedberg) or ‘S’ value.
