List of most probable exam, interview and viva questions on Immunology
Q.1. What do you mean by Immunology?
Ans. Immunology is the study of specific resistance to further infection by a particular microorganism or its product’s Immunology is the science which deals with the body’s response to antigenic challenge.
Immunology, the study of the immune system, grew out of the common experience that people who recover from certain infections become there after “immune” to the disease. Immunity is highly specific: an individual who recovers from measles is protected against the measles virus but not against other common viruses such as cold, chicken- pox or mumps.
Normally, many of the responses of the immune system initiate the destruction and elimination of invading organisms and any toxic molecules produced by them. Because these immune reactions are destructive in nature, it becomes necessary that they be made in response only to molecules that are foreign to the host and not to those of the host itself.
This ability to distinguish foreign molecules from self molecules is another fundamental feature of the immune system. However, occasionally it fails to make this distinction and reacts destructively against the host’s own molecules; such autoimmune diseases can be fatal to the organism.
Almost any macromolecule (e.g., protein, most polysaccharides and nucleic acids), as long as it is foreign to the recipient, can induce an immune response; any substance capable of eliciting an immune response is called an antigen (antibody generator).
Q.2. What are the contributions of scientists in the field of Immunology?
Ans. Some eminent scientists and their contributions to the field of immunology starting from thucididas of the time before Christ up to the late 20th century Immunologists.
Pointed out that the people who were once attacked by the plague could tend the sick without the fear of the second attack of the disease.
Jenner in 1878 used non virulent cowpox vaccine against small pox infection. So that Edward Jenner was the first one who prepared vaccine against small pox.
The next great discovery in the field of Immunology is that of the French chemist Louis Pasteur. He worked on a common of the animals such as pebrine (disease of silk worm) anthrax (disease of cattle), Chicken cholera (disease of fowls) and rabies. Pasteur tried a successfully using attenuated organism against anthrax.
In 1883 he suggested the role of phagocytes in Immunity. In 1908 shared Nobel Prize with Ehrich for his contribution to Immunity.
In 1890 he recognized antibodies in serum against diphtheria toxin.
He developed diphtheria Immunization and antiserum therapy.
He discovered the occurrence of a time lag after antigen injections before antibody was formed. He also found out that Immunity could be transferred from mother to offspring.
Received Nobel Prize in 1945 for his discovery of penicillin, discovery of antibiotic.
Introduced diagnosis of a disease by blood test. Devised the blood known as widal’s for the diagnosis of typhoid fever.
Karl Land Steiner:
Discovered the four primary blood groups in man namely A, B, AB, and O.
Introduced fluorescence antibody technique.
Discovered acquired Immunologic tolerance.
Portar and Edelman:
Determined structure of Immunoglobulin.
Introduced radioimmunoary in 1977.
Q.3. What is the concept of Immunology?
Ans. Human body is capable of resisting different types of organisms or toxins that can damage organs or tissues. The body can also prevent recurrence of certain infectious diseases. The capacity of an organism to resist development of disease is called immunity. This ability is of vital importance because the body is exposed to pathogens from the moment of birth. The study of immunity is immunology.
The immune system is composed of cells that can engulf bacteria, kill parasites or tumour cells, or kill viral-infected cells. The different interdependent cell types collectively protect the body from bacterial, parasitic, fungal, viral infections and from the growth of tumour cells. Many of these cell types have specialised functions.
The human body has various ways of stopping pathogens from getting into the body. There are two types of defense mechanisms to fight invaders – the non-specific defense mechanism or innate immunity and the specific defense mechanisms or acquired immunity.
Q.4. What do you understand by Blood Types and Immunology?
Ans. The antigens found in the surface of the red blood cells are called agglutinogens. They cause agglutination reaction in the presence of specific antibodies known as agglutinins. Therefore during blood transfusion, proper matching of the donor and recipient must be done. If a transfusion is made between an incompatible donor and recipient, the recipient’s blood will undergo a cascade of events. Reaction between the antigens and antibodies will produce chumping that will clog the capillaries, burst cells and release hemoglobin. This will crystallize in the kidney and lead to kidney failure.
Similarly Rh incompatibility (Fig. 13) also leads to agglutination. To avoid Rh sensitization, shortly after each birth of an Rh +ve baby, the Rh -ve mother is given an injection of anti-Rh antibodies or anti-D. The preparation is called Rh immune globulin (RhIG) or Rhogam. These passively acquired antibodies destroy any fetal cells that got into her circulation before they can elicit an active immune response in the mother.
Tiselius and Kabat in 1938 demonstrated that the antibody activity is associated with the gamma globulin, fraction of the blood serum. But later researches have shown that not only gamma globulin but also the other fractions of serum globulins show antibody activity. Hence the scrum globulins which are immunologically active are termed as immunoglobulins.
(i) There are two types of light chain namely kappa (k) and lambda (X) based on their structure and amino acid sequence. But, in any one of the immunoglobulin molecule, both the light chains are of the same type.
(ii) Based on the presence of type of light chain the immunoglobulin molecules are of two types namely H type and L type. Approximately 60% of the serum immunoglobulin molecules are H type while only 40% are L Type.
(iii) The H chain is structurally and antigenetically distinct for each class and designated by Greek letter as follows:
The L chain is attached to the H chain by disulfide bond. The two H chains are joined together by one to Five S-S bonds, depending upon the class of immunoglobulins.
(i) Immunoglobulins are defined as proteins of animals’ organ.
(ii) Immunoglobulins are synthesized by plasma cells and also by lymphocytes. Immunoglobulins make 20 to 25 percent of the total scrum protein. The term immunoglobulin is the structural and chemical concept while antibody is biological and functional concept.
All antibodies are immunoglobulins but all immunoglobulins may not be antibodies.
Q.6. What is the structure of Immunoglobulin?
Ans. Porter (1962) has proposed a basic four chain structure for the immunoglobulin molecule.
According to that each molecule of immunoglobulin is formed of 2 pairs of Polypeptide chains joined by disulfide bond.
(i) Each immunoglobulin molecule consists of two identical small chains known as light
(ii) Each of the light and heavy chains have two terminal ends called N terminal end or amino terminal end and the C terminal end or carboxy terminal end.
(iii) Each light chain has about 214 amino acids and a molecular weight of 25,000 daltons, whereas each heavy chain is about twice as long as. The light and the molecular weight is about 50,000 daltan.
The Human immunoglobulin G (IgG) may be considered as a typical example of basic antibody structure. It consists of 2 light chains and 2 heavy chains. A study of the amino acid sequence of the light chain has shown that each light chain has two distinct regions.
The carboxy terminal half of the chain which contains approximately 107 amino acid residues is constant in its amino acid sequence and hence called the constant region(CR) whereas the other half namely the amino terminal half of the chain shown much variability in the amino acid sequence and is known as the variable region(VR).
It is composed of carboxy terminal portion of H chain. It determines biological properties of immunoglobulin molecules. It contains carbohydrate. It is crytallizable.
It is amino terminal half of heavy chain and one light chain. It does not crystallize. It does not contain carbohydrate and act as antigen binding fragment.
Q.7. What are the main functions of Immunoglobulin?
Ans. The important functions of immunoglobulins are:
1. Complement activation causing lysis
2. Prevention of attachment of microbe to host cells
3. Neutralize toxin
4. Motility of microorganisms is restricted.
5. Ultimately may result in agglutination of microbes.
Q.8. What are the classes of Immunoglobulin?
Ans. 1. Ig G:
(i) It is the major serum immunoglobulin.
(ii) It has molecular weight of 1,50,000.
(ii) It has half-life of 23 days.
(iv) The normal serum concentration of IgG is 5 to 16 mg/ml.
(v) It passes through placenta and provides natural passive immunity.
(vi) It participated in Immunological reactions like precipitation, complement fixation, neutralization of toxin and viruses.
(i) It constitutes 10% of total serum globulin.
(ii) Normal serum level is 0.6 to 4.2 mg/ml.
(iii) It has half-life of 6 to 8 days and molecular weight is 160000 Daltons.
(iv) It is found in high concentration in colostrums, tear, bile saliva, intestinal and nasal secretions.
(v) It does not passes through placenta.
3. Ig M:
(i) It is also called macroglobulin
(ii) It constitutes 5 to 10 % serum globulin (05 to 2mg/ml).
(iii) It has molecular weight of 9,00,000 to 10,00,000 Dalton.
(iv) It has half-life is 5 days and does not passes through placenta.
(v) It is more efficient in agglutination.
4. Ig D:
(i) It is present in concentration of 0.03 mg/ml.
(ii) It has half-life of 3 days.
(iii) It is present on the surface of B lymphocytes.
(iv) It acts or recognition receptor for antigens cell membrane.
5. Ig E:
(i) It has molecular weight of 1,90,000 Dalton.
(ii) Its half-life is 2 days.
(iii) It is activated by heat at 56°c for 1 hour.
(iv) It does not pass through placenta.
(v) Elevated levels are seen in asthma, high fever and eczema.
Ans. 1. It helps us to understand etiology and pathogenesis if disease e.g. rheumatic fever, asthama etc.
2. Diagnosis of disease.
3. Development of vaccine
4. Treatment using antibodies.
5. Transplantation and blood transfusion.
Immunity is concerned with resistance to infection. This is carried out by the process of recognition and disposal of foreign material that enters the body.
“The resistance offered by the host to the harmful effect of pathogenic microbial infection is called Immunity.”
Immunity is broadly classified in to two types, namely innate and acquired immunity.
(i) Innate Immunity:
This is a basic Immunity which may be genetically passed on from one generation to other generation. It does not depend or prior contacts with microorganisms. It may be specific when it shows resistance to particular pathogens. It may be non-specific when it indicates a degree of resistance to all infection.
(ii) Acquired Immunity:
The Immunity acquired during the life time of an individual is known as acquired immunity.
1. Active Immunity:
It is the resistance developed by immunity as a result of antigenic stimulus. Active immunity may be.
Natural Active Immunity:
This is acquired after one infection or recovery from disease or Clinical infection after repeated exposure to small doses of the infecting organisms.
Artificial Active Immunity:
It may be acquired artificially by inoculation of bacteria, viruses or their products as follows.
After proper attenuation e.g. Smaller BCG.
Attenuation may be obtained as follows:
1. Subjecting the organism to drying e.g. rabies virus vaccine
2. Growing the organism at temperature higher than optimum e.g. Pasteur’s anthrax vaccine.
3. By passage through animals of different species e.g. Variola virus through rabbit and calf.
4. By continued cultivation in presence of antagonistic substance, e.g. BCG Vaccine preparation by prolonged cultivation of tubercle bacillus (bacillus calmette and Guerin) in medium containing bile.
B:-Organisms are killed by heat or phenol without changing the antigenic structure of bacteria e.g. Typhoid vaccine, cholera vaccine.
Bacterial inactivated toxin (not toxigenic but retains antigenicity) is injected repeatedly in increasing doses e.g. Diphtheria and tetanus.
2. Passive Immunity:
Here subject is immunized by prepared antibodies and body cells do not take any active part in the production of immunity.
It is following types:
A:-Natural Passive Immunity:
During intrauterine life transmission of antibodies from the mother to fetur can occur through placenta.
It may be by the way of colostrums of mother and milk during first few months of life. These antibodies last for few weeks and protect infants from diphtheria, tetanus, measles, mumps, small pox, etc.
B:-Artificial Passive Immunity:
Immunization in this care is passive and produced by injection of serum of animals that have been immunized actively.
Antibodies remain in effective quantity for 10 days only following serum may be used:
It is produced by injection of toxic into horse in increasing doses till the blood is rich in circulating antibodies serum is separated. This serum contains prepared antibodies.
Antibodies are produced by injection of bacterial into animal and serum is collected e.g. preumococcal, meningococcal, anthrax etc.