Thursday, 7 January 2016

Most recent asked Immunology Interview Questions and Answers

51. What are the applications of precipitation reactions?
1.    Precipitation reaction is the basic reaction for a number of techniques.
2.    It is less sensitive for detecting antibodies.
3.    Precipitation reactions in gels have several advantages rather than in liquid medium.
4.    They have forensic application in identification of blood and seminal stains.

52. What is zone of equivalence?
In this, ratio of antigen-antibody is seen optimal which results in large multimolecular lattice, hence maximum precipitation is observed.

53. What is zone of antibody excess?
In this, the first available antigen is completely filled by antibody molecules. Hence, no antigenic determinant is left out free. Unreacted antibody is seen in large amount, hence poor lattice formation.

54. What are the three distinct phases that a precipitation shows?
The three distinct phases are
Ascending part called ‘zone of antibody excess’.
A peak called ‘zone of equivalence’.
A descending part called ‘zone of antigen excess’.

55. Give the mechanism of precipitation.
Marrak proposed the lattice hypothesis to explain the mechanism of precipitation.
The amount of precipitate formed is greatly influenced by relative proportions of antigens and antibodies.
The valency of antigens is multivalent.
When antigen-antibody is in optimal concentration, the precipitation is complete. So that, large lattice is formed.

56. Briefly describe about precipitation reaction.
When a soluble antigen combines with corresponding antibody in the presence of electrolyte at a suitable temperature and pH, the antigen-antibody complex forms an insoluble precipitate .Antibodies that form precipitate ate called precipitants.

57. Into how many types is antigen-antibody reactions are broadly classified?
It is broadly classified into five-
1.    Precipitation
2.    Agglutination
3.    Complement fixation
4.    Immunoassay using labeled reagents
5.    Immunohistrochemistry (Immunoflourescence)

58. What is horseman antigen?
The glycolipid antigens are present in most tissues of guinea pigs but not in the RBC. They are found in gastrointestinal mucosa in some people. This horseman antigen will not induce antibody formation.

59. What are heterophile antigens?
Heterophile antigens are polysaccharides, which are structurally similar because of their limited complexity. They are derived from members of widely separated taxonomic groups.

60. Give an example of cross-reaction.
Cross reactivity is often observed in polysaccharide antigens that contain similar oligosaccharide residue. A, B, O blood group antigens - These are glycoprotein expressed on RBC.

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