Immunology Interview Questions & Answers

Question 1. What Is Immuno Electrophoresis?

Answer :

The resolving power of immuno diffusion was greatly enhanced bye immuno electrophoresis. This involves the electrophoretic separation of antigen into its constituent proteins followed by immuno diffusion.

This technique is performed on 1% agarose gel. Antigen mixture is first electrophori zed and separated based on charge, troughs are then cut in the agarose gel, and antiserum is added to the troughs.

The agarose gel is then incubated 1824hrs during which the antigen and antibody diffuse towards each other. The formation of precipitin bands can be observed for the individual antigen components.

Question 2. How Is Immuno Electrophoresis More Advance Than Paper Electrophoresis?

Answer :

In paper electrophoresis, serum proteins can be separated into 5 different bands but the same protein using immuno electrophoresis can be separated into 30 different proteins.

Question 3. Give Some Applications Of Immuno Electrophoresis?

Answer :

1. This technique is useful for testing normal and abnormal proteins in serum and urine.
2. It is useful to determine whether a patient produces abnormally a low amount of one or more proteins.
3. It is also used if a patient over produces some serum proteins.

Question 4. What Is Counter Current Immuno Electrophoresis?

Answer :

This technique involves the simultaneous electrophoresis of antigen and antibody in the gel in the opposite direction resulting in precipitation of point where there is optimum concentration of antigenantibody.

This method produces visible precipitin with in 30 minutes and is 10 times more sensitive than the standard double diffusion technique.

Question 5. Give Application Of Counter Current Immuno Electrophoresis?

Answer :

This technique is applied to detect the antibody against hepatitisB and to detect antibodies against SLE (systemic leupus erythromotosis) and used to detect specific antigen foemeningo coccus in cerebrospinal fluid.

Question 6. What Is Immuno Fluorescence?

Answer :

Fluorescence is the property of absorbing light ray of particular wavelength and emitting rays in different wavelength.

Antigens that are bound to cells or tissue sections can be visualized by tugging the antibody molecule with a fluorescent dye or fluorochrome.

Question 7. What Are The Most Commonly Used Fluorescent Dyes?

Answer :

The most commonly used fluorescent dyes are fluorescin or rhodamine. Both dyes can be conjugated to Fc region of antibody without affecting the specificity of the antigen.

Question 8. Into How Many Types Is Immuno Fluorescence Is Divided?

Answer :

Immuno fluorescence is divided into 2 types

1. Direct immuno fluorescence
2. Indirect immuno fluorescence

Question 9. What Are Heterophile Antigens?

Answer :

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

Question 10. What Is Horseman Antigen?

Answer :

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.

Question 11. Into How Many Types Is Antigen-antibody Reactions Are Broadly Classified?

Answer :

It is broadly classified into five.

1. Precipitation
2. Agglutination
3. Complement fixation
4. Immunoassay using labeled reagents
5. Immunohistrochemistry (Immunoflourescence)

Question 12. Briefly Describe About Precipitation Reaction?

Answer :

When a soluble antigen combines with corresponding antibody in the presence of electrolyte at a suitable temperature and pH, the antigenantibody complex forms an insoluble precipitate Antibodies that form precipitate ate called precipitants.

Question 13. Give The Mechanism Of Precipitation?

Answer :

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 antigenantibody is in optimal concentration, the precipitation is complete. So that, large lattice is formed.

Question 14. What Are The Three Distinct Phases That A Precipitation Shows?

Answer :

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’.

Question 15. What Is Zone Of Antibody Excess?

Answer :

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.

Question 16. What Is Zone Of Equivalence?

Answer :

In this, ratio of antigenantibody is seen optimal which results in large multimolecular lattice, hence maximum precipitation is observed.

Question 17. What Are The Applications Of Precipitation Reactions?

Answer :

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.

Question 18. What Are Immuno Diffusion Reactions?

Answer :

These reactions can be used to determine relative concentrations of antigens and antibodies to compare antigens and to determine the relative purity of an antigen. They are mainly preformed in 1% agarose gels.

Question 19. Name The Two-immuno Diffusion Techniques?

Answer :

• Radial immuno diffusion method and
• Double immuno diffusion in two dimensions

Question 20. What Is Radial Immuno Diffusion Method?

Answer :

It is used to qualitate the antigen. Suitable dilution of antiserum is incorporated in the agar gel. Antigen is added to the wells cut on the surface of the gel. As the antigen diffuses into the agar region, equivalence is established and ring of precipitation is formed. The area of precipitin ring is directly proportional to the concentration of antigen. By comparing the area of precipitin with a standard curve obtained by measuring the precipitin area of known concentration of antigen, the concentration of antigen in the given sample can be determined.

Question 21. What Is The Limitation For Radial Immuno Diffusion Method?

Answer :

This method cannot the antigens present in concentration below 510 micro grams/ml.

Question 22. What Is Double Immuno Diffusion Method?

Answer :

In this method, both antigens and antibodies diffuse radically from wells towards each other by establishing a concentration gradient. As equivalence is reached, a visible line of precipitation is observed.

The patterns of precipitin lines that are formed when two different antigens are placed in adjacent wells indicate whether they share any common epitope or not.

Identity occurs when two antigens share identical epitopes; hence, the line of precipitation formed by them will fuse to give single curve line of identity.

Nonidentity occurs when two antigens are unrelated. The antiserum form independent precipitin lines that cross each other.

Partial identity occurs when two antigens share common epitope. The antiserum forms line of identity with the common epitope and a curved spur with the unique epitope.

Question 23. What Is An Epitope?

Answer :

The smallest unit of antigenesity is known as antigenic determinant or epitope. The part of the antigen at which the antibody reacts is known as epitope or antigenic determinant.

It is a small area possessing specific chemical structure and stereo configuration on the antigen capable of sensitizing on immuno site and of reacting with its complimentary site on the specific antibody.

Question 24. What Is A Paratope?

Answer :

The portion of the antibody molecule that binds to the epitope is called as paratope. Epitope and paratope determine the specificity of immunological reactions.

Question 25. What Are The Forces That Are Responsible For Antigen-antibody Reactions?

Answer :

The process that holds antigenantibody together is called nonspecific interactions. Inter molecular forces may be classified into four1.

1. Electrostatic bonds
2. Hydrogen bonds
3. Hydrophobic interactions
4. Vander Val interactions

Question 26. Explain In Brief About Electrostatic Bonds In Antigen-antibody Interaction?

Answer :

These are formed due to the attraction between opposite charged protein side chains.

Question 27. Explain In Brief About Hydrogen Bonds Antigen-antibody Interaction?

Answer :

Reversible hydrogen bonds are formed between hydrophilic groups such as hydroxyl, amino and carboxylic group. Although hydrogen bonds are relatively weak, they play an important role in interaction of antigenantibody.

Question 28. Explain In Brief About Hydrophobic Interactions In Antigen-antibody Interaction?

Answer :

Contribute up to 50% of the total strength of antigenantibody interactions. These reactions are found when ever the side chains of nonpolar amino acids of antigenantibody come together.

Question 29. Explain In Brief About Vander Val Interactions In Antigen-antibody Interaction?

Answer :

Temporary transfer of electrons from one molecule to another will result in the force of attraction between them. This is seen when the interacting molecules come close to each other.

Question 30. What Is Affinity Of An Antibody?

Answer :

The strength of binding of an antibody to a monovalent antigen or single antigenic determinant is called affinity of an antibody.

Question 31. What Is Avidity?

Answer :

The capacity of an antiserum containing various antibodies to combine with the whole antigen is called avidity. Thus, avidity is used to denote the overall capacity of an antibody to combine with multivalent antigen.

A multivalent antigen has many types of antigenic determinants, when this is injected into the blood each antigenic determinant stimulate the production of particular antibody.

Question 32. What Is A Cross-reaction?

Answer :

Antigenantibody reactions are specific, but in some cases antibody elicited by one antigen can cross react with another antigen. This reaction is called as crossreaction and the antigen that produces crossreaction is called as crossreactive antigen. Crossreaction is due to the presence of two or more antigenic determinants on the related antigen.

Question 33. Give An Example Of Cross-reaction?

Answer :

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.

Question 34. Give The Classification Of Hypersensitivity?

Answer :

Hypersensitivity is classified into five types:

1. Anaphylaxis
2. Antibody dependant cytotoxicity
3. Immune complex mediated diseases
4. Delayed type ‘o’ cell mediated hypersensitivity
5. Stimulatory hypersensitivity

Question 35. What Is Anaphylaxis?

Answer :

It is most rapid hypersensitive reaction. It responds within minutes of applying a stimulus and can get localize. Reactions are mediated by release of pharmacologically active substances.

Question 36. What Is Hypersensitivity?

Answer :

The inflammatory response produced by inflammatory molecules result in tissue damage and some times even death. We call this as hypersensitivity or allergy.

Question 37. What Is Delayed Hypersensitivity?

Answer :

We can recognize the Symptoms only days after exposure. This is delayed hypersensitivity (DTH).

Question 38. What Is A Myeloma Protein?

Answer :

It is a monoclonal immunoglobulin produced from a myeloma cell.

Question 39. What Is Opsonin?

Answer :

Opsonin is a substance, which promotes phagocytosis of antigens by binding to them.

Question 40. What Is An Incomplete Antibody?

Answer :

Antibody can bind to an antigen but cannot induce agglutination is called incomplete antibody.

Question 41. What Are Iccosomes?

Answer :

The particles coated with immune complexes and are released from follicular dendritic cell extensions, are called as iccosomes.

Question 42. Name The Scientists Who Classified Hypersensitivity?

Answer :

Coombs and Gell.

Question 43. What Are Hypersensitive Reactions?

Answer :

If humoral or cellular immunity is switch on to high for length of time, tissue damage may occur. Such reactions are called hypersensitive reactions.

Question 44. What Is Auto Immunity?

Answer :

Disease caused by immunological reaction to selfantigen. Such type of diseases is classified either organ specific or nonorgan specific.

Question 45. Name Some Of The Immuno Suppressive Agents?

Answer :

• Cytotoxic agents such as chlorambucil, cyclophosphamide, and azathioprine
• Glucocorticoids
• Cyclosporine
• Antilymphocyte antibodies

Question 46. What Is Immuno Suppression?

Answer :

Immuno suppression is particularly given to the patients who are undergoing organ transplantation in the treatment of autoimmunity, graft rejection and in allergy conditions.

Question 47. What Are The Types In Adjuvants?

Answer :

1. Organic adjuvants
2. Synthetic adjuvants
3. Tuftsin

Question 48. What Is An Adjuvant?

Answer :

Adjuvant potentates the immune response Vaccines need to be enhanced by some substances, these substances are called adjuvants.

Question 49. What Is Vaccination?

Answer :

Vaccination means exploiting the immune system to protect against infectious diseases. Vaccination is done to protect against lethal diseases such as mumps, rubella, poliomyelitis, diphtheria, tetanus, small pox etc.

Question 50. What Is Attenuation?

Answer :

Natural behavior of an organism without causing disease is called attenuation i.e. reducing pathogenesity of the organism.

Question 51. What Is Secondary Immune Response?

Answer :

Secondary immune response occurs when second exposure to the same antigen occurs after weeks, months or after years.

Question 52. What Is Inductive Or Latent Period?

Answer :

After immunogen is introduced no antibody is detected, this is latent or inductive period. In this period, immunogen is recognized as a foreign substance.

Question 53. What Is Primary Immune Response?

Answer :

First exposure to an antigen produces primary immune response.

Question 54. What Is A Binder?

Answer :

The binding protein (usually antibody) which binds to the ligand is called as binder.

Question 55. What Is An Analyte Or Ligand?

Answer :

The substance whose concentration is to be determined is called as an analyte or ligand.

Question 56. What Is Importance Of Radio Immuno Assay?

Answer :

It is the most sensitive technique used for detecting antigen or antibody. This type of reaction is also called as binder ligand assay.

Question 57. In Radio Immuno Assay What Is The Used To Label An Antigen?

Answer :

In this technique, the antigen is generally labeled with aemitting isotopes such as I125.

Question 58. What Is Radio Immuno Assay?

Answer :

It is a competitive binding assay in which fixed amount of antibody and radiolabelled antigen react in the presence of unlabelled antigen.

Question 59. What Is Western Blotting?

Answer :

Identification of specific protein in a complex mixture of proteins can be accomplished bye a technique that is known as western blotting.

Question 60. What Are The Enzymes Used For Labeling Of Antibodies?

Answer :

Enzymes used for labeling of antibodies are horseradish peroxidase, alkaline phosphatase, ßgalactosidase, lacto preoxidase, etc.

Question 61. What Is The Signi&cance Of Indirect Elisa?

Answer :

It is used for the detection of the presence of serum antibodies against immuno deficiency virus (HIV, the causative agent of AIDS).

Question 62. In How Many Ways Elisa Can Be Carried Out?

Answer :

It can be carried out in three ways.

• Indirect ELISA
• Sand witch ELISA
• Competitive ELISA

Question 63. What Is The Signi&cance Of Elisa?

Answer :

It is used for the detection and for identification of either antigen or antibody.

Question 64. Name Two Enzymes That Have Been Employed For Elisa?

Answer :

1. Alkaline, phosphatase, horseradish, preoxidase
2. Para nitro phenyl phosphatase

Question 65. What Is The Basic Principle Of Elisa?

Answer :

The basic principle is an enzyme conjugated to n antibody reacts with a colorless substrate to generate a colored product.

Question 66. What Is The Full Form Of Elisa?

Answer :

Enzyme Linked Immuno Sorbant Assay.

Question 67. What Are The Uses Of Indirect Immuno Fluorescence?

Answer :

1. For identifying bacterial species
2. Detecting antigenantibody complexes in autoimmune diseases
3. Detecting compliment components in tissues.
4. Localizing hormones

Question 68. What Are The Advantages Of Indirect Immuno Fluorescence?

Answer :

The primary does not need to be conjugated with label.

It increases the sensitivity of staining because multiple fluorochrome reagents will bind to each antibody molecule.

This method has great flexibility.

Question 69. What Is Indirect Immuno Fluorescence?

Answer :

In a method the primary unlabelled antibody is detected with a number of reagents have been developed for indirect staining. The most common is fluorescence labeled anti isotype antibody such as fluoroscin labeled goatmouse antibody.

Question 70. What Is The Disadvantage Of Direct Immuno Fluorescence?

Answer :

A separate fluorescent conjugate have to be prepared against each antigen to be tested.

Question 71. What Is Direct Immuno Fluorescence?

Answer :

In this method, the species antibodies are primary antibodies, which are directly conjugated to fluorescent dye.

Question 72. What Is Antigenic Specificity?

Answer :

Antigen antibody reaction is specific and specificity is determined by special configuration of antigenic determine.

Question 73. Give Some General Features Of Antigen-antibody Interaction?

Answer :

1. The reaction is specific and antigen combines only with its corresponding antibody and vice versa.
2. Entire molecules react but not the fragment.
3. There is no denaturation of antigen or antibody during the reaction.
4. The combination of antigen – antibody is firm but reversible. The firmness of the reaction is influenced by the affinity and avidity of the reaction.
5. Both antigens and antibodies participate in the formation of agglutination and precipitation reactions.
6. Antigens and antibodies can combine in various proportions unlike chemicals with fixed valancy.

Question 74. What Is An Antigen And Antibody Interaction?

Answer :

Antigenantibody interaction is similar to an enzyme substrate interaction. The reaction between antigen and antibody occurs in two stages. Primary stage is the initial interaction of antigenantibody without any visible effect .The reaction is rapid and obeys the general law of thermodynamics and physical chemistry.

The primary stage is followed by the secondary stage leading to demonstrate events such as precipitation, lysis of cells, neutralization of toxins and fixation of compliments etc.

Question 75. Briefly Describe About Dosage And Route Of Administration, Which Make A Substance Antigenic?

Answer :

Combination of optical dosage and routes of administration will induce a peak immune response in a given animal. An insufficient dose will not stimulate an immune response. An excessive dose does not give a peak immune response because it causes a state of immunological unresponsiveness or nonresponse known as immunological tolerance.