Questions - Answers
Very Short Answer Type Questions
1. Define the terms immunity and immune system.
A: a) The ability to resist or eliminate harmful foreign microbes and their products is known as immunity.
b) The network of organs, cells and proteins that protect the body from harmful foreign microbes and their products is known as immune system.
2. Define the non specific lines of defence in the body.
A: Out of the three defence lines of immunity
a) First line - e.g.: Lysozyme of saliva and
b) Second line - e.g.: Phagocytes and NK cells are the non specific lines.
3. Differentiate between mature B cells and functional B cells.
A: a) Mature B - cells produce antibodies. As these antibodies take antigens, B cells are called immunocompetent B - cells.
b) The functional B - cells are of two types, namely, plasma cells (long lived and store information about the specific antigen) and plasma cells (produce antibodies)
4. Write names any four Mononuclear phagocytes.
A: Histiocytes, Kupffer cells, Microglia and Osteoclasts.
5. What are complement proteins?
A: A group of inactive plasma proteins and cell surface proteins is called complement proteins.
6. "Colostrum is very much essential for new born infants". Justify.
A: a) Colostrum is the first milk produced by mother after child birth.
b) It contains antibodies like IgA which provide immunity to the new born.
7. Differentiate between perforins and granzymes.
A: a) Perforins form pores to the cell membrane of infected cells.
b) Granzymes enter the infected cells through these pores and initiate reactions that destroys the infected cell.
8. Explain the mechanism of vaccination or immunisation.
A: Vaccination is the process in which inactivated or weakened pathogens or antigenic proteins of the the pathogen are introduced into the body of the host. They initiate the production of appropriate antibodies in the host.
9. Mention various types of immunological disorders.
A: a) Primary immuno deficiency disorders. These are caused by defective genes.
e.g.: Severe Combined Immuno Deficiency (SCID)
b) Secondary immuno deficiency disorders - These are caused by various factors like infections, ageing etc.
e.g.: HIV/AIDS.
10. "More and more people in metrocities of India are prone to allergies". Justify.
A: More and more people in metropoliton cities of India suffer from allergies leading to asthmatic attacks due to environmental pollution. This is because they are exposed to various types of pollutants that cause allergies and health problems.
11. What are autoimmune disorders? Give two examples.
A: In some cases, our immune system fails to recognise some of our own body proteins and treats them as foreign antigens that results in attacks on our own tissues. This leads to serious diseases called auto immune diseases.
e.g.: Graves disease, Rheumatoid arthritis.
12. How can the graft rejections be avoided in patients?
A: a) Tissue matching and blood group matching should be done before grafting.
b) After grafting, the patient should be give immuno supressant drugs.
Short Answer Type Questions
1. Write short notes on B cells.
A: B - Lymphocytes (B - cells): These lymphocytes are capable of producing antibodies and capture the circulating antigens. They are produced from stem cells in the bone marrow in adults and in foetus, from liver (from bursa fabrici in birds). Mature B - cells produce antibodies. As these antibodies take antigens, they are called immuno competent B - cells. The mature B - cells enter the secondary lymphoid organs and then become two types of functional cells, namely memory cells (long lived and store information about specific antigen for quick response) and plasma cells (produce specific antibodies).
2. Write short notes on immunoglobulins.
A: Immunoglobulins or antibodies: Whenever antigens enter the body, B - lymphocytes produce antibodies, that bind to the antigens and destroy them. Antibodies are highly specific.
i. An antibody consists of four polypeptide chains, viz, two light chains (L) and two heavy chains (H). The H chain and L chain are linked by disulphide bonds to form Y - shaped molecule.
ii. The ends of two arms of Y are called variable regions.
iii. The distal end of each arm of Y is known as Fab region, which binds to antigen.
iv. The lower parts of arms are called constant regions (C).
v. The stem of Y is known as Fc region. It binds to the complement proteins or Fc receptors of cells (like phagocytes, mast cells etc.,).
* The part of antibody that recognises and attached to antigen is known as paratope. The portion of antigen that binds to paratope is called epitope.
vi. Based on the type of heavy chain, antibodies are classified to five types, namely, IgM, IgG, IgD, IgA and IgE.
vii. Antibodies are of two types.
* Membrane bound antibodies - Present on cell membrane of immuno competent B - cells.
* Secreted antibodies - Circulate in the body fluids.
3. Describe various types of barriers of innate immunity.
A: Innate immunity: It is the inborn resistance to diseases. It consists of four types of barriers.
a. Physical barriers - Skin, mucus membranes etc.
b. Physiological barriers - HCl in stomach, saliva in mouth, tears in eye etc.
c. Cellular barriers - Polymorpho neuclear leucocytes, monocytes, NK cells etc.
d. Cytokine barriers - Secreted by the immune cells protect non infected cells from infected cells.
4. Explain mechanism of humoral immunity.
A: Humoral Immunity: Immunity mediated by antibodies that are released into body fluids (e.g.: plasma, lymph) is called humoral immunity. It involves the interaction of B - cells with free antigens.
Mechanism:
i. In secondary lymphoid organs, the free antigens bind to Fab end of the antibodies that are present on the surface of mature B - cells.
ii. B - cells engulf and process the antigens.
iii. Then they display the antigenic fragments on their membrane with the help of class II - MHC molecules.
iv. Then appropriate TH cells recognise them and interact with the antigen MHC - II complex and release a type of interleukin, which stimulates the B - Cells to proliferate and differentiate into memory cells and plasma cells.
v. The plasma cells release specific antibodies into the plasma or ECF.
vi. These antibodies help in opsonising and cross linking of antigens leading to agglutination of insoluble antigens and precipitation of soluble antigens.
vii. They also activate the phagocytes and complement system.
* The products of antigen and antibody reactions are known as antigen - antibody complexes or immuno - complexes, which are removed by oesinophils and monocytes.
5. Explain mechanism of cell mediate immunity.
A: Cell Mediated Immunity: Immunity mediated by the activated T - cells, NK cells etc., is known as cell mediated immunity. It does not involve antibodies.
Mechanism: Antigen presenting cell engulf the antigens. It processes the antigen and displays antigenic fragment on their membrane, bout to class II MHC molecule. TH cell recognises and interacts with antigen class II MHC molecule complex. Activated TH cells secrete interleukin - 2.
Tc cells bind to antigen class I MHC molecule complex on altered self cells. Interleukin - 2 causes proliferation and differentiation of antigen activated Tc cell into a clone of effector CTLs. CTLs attach to appropriate target cells and release perforins and granzymes. Perforins form pores on the target cell membrane. Granzymes enter the target cells and initiate reactions that distroy the infected cell DNA. Some Tc cells remain as long lived memory T cells.
6. Explain the mechanism by which HIV Multiplies and leads to AIDS.
A: i. After infection to a person the HIV enters the TH cells macrophages or dendric cells.
ii. In these cells, the ss RNA synthesises a DNA strand complementary to viral RNA in presence of reverse transcriptase.
iii. Reverse transcriptase catalyses the synthesis of another strand of DNA and thus a double strand DNA is formed.
iv. This viral DNA gets incorporated into the DNA of the host cell with the help of viral enzyme - integrase.
v. Transcripted RNA from this DNA will act as the genome for the new or it can be transmitted into viral proteins.
vi. Now the infected host cells act as HIV generating factories. New viruses are bud off from the host cell.
vii. As a result, progressive decrease in the number of TH cells of the infected person leading to immuno deficiency.
viii. Attack on certain types of cells or tissues only by viruses such as HIV is referred to as tissue tropism.
