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Right ANSWER is (c) increase in CALCIUM ions

To explain I would SAY: When the antigen-presenting cells – dendritic cells display fragments of antigens on their surface in the lymph nodes, the binding with a particular T-cell receptor occurs that leads to activation of the latter. The activation is ASSOCIATED with a TRANSIENT increase in cytosolic calcium concentration.

The CORRECT CHOICE is (b) False

The best EXPLANATION: Plasma cells are differentiated from the B-cells (PRECURSORS) and contain an extensive network of rough endoplasmic reticulum to provide for the excessive protein synthesis involved in antibody production.

Right ANSWER is (c) fragments of antigens

The EXPLANATION: Unlike B-cells, T-cells do not REQUIRE intact antigens for ACTIVATION rather small fragments of antigens. The antigen-presenting cells display fragments of antigens on their SURFACES that can be recognized by the T-cell receptors.

Right answer is (c) TOXOID

To explain I WOULD say: Tetanus is caused by an anaerobic soil bacterium KNOWN as CLOSTRIDIUM tetani. For immunity against tetanus, infants are inoculated with a harmless version of the tetanus neurotoxin – toxoid.

Correct option is (c) lymphocytes

The best I can explain: Humoral immunity is the falls under the ADAPTIVE IMMUNE response and is MEDIATED by the antibody-secreting B-lymphocytes. The antibodies are globular, blood-borne proteins of the IMMUNOGLOBULIN superfamily.

Right option is (d) multiple myeloma

Explanation: In multiple myeloma, the plasma cells go out of CONTROL and convert into MALIGNANT cells. The plasma cells make an abnormal ANTIBODY in this disease, the ANTIBODIES are known by several names – monoclonal immunoglobulin, monoclonal protein etc.

Right CHOICE is (c) chemoattractants

For explanation: CHEMOKINES are a small family of cytokines that are powerful chemo-attractants that STIMULATE and regulate the migration of lymphocytes into the INFLAMMATION sites.

The correct option is (a) Type I

The BEST I can explain: In a type of antiviral response initiated within the CELL, type I interferons (IFN-alpha and IFN-beta) are PRODUCED and secreted into the extracellular space where they bind to noninfected cells and RENDER them resistant to subsequent VIRAL infections.

Correct choice is (a) suppresses the immune system

Best explanation: Cyclosporin A is a drug that suppresses immune system FOLLOWING transplant SURGERY. It is a CYCLIC PEPTIDE produced by a soil fungus that inhibits the phosphatasein the signaling pathway that leads to the PRODUCTION of cytokines.

Correct CHOICE is (a) Cytotoxic T lymphocytes

The best I can EXPLAIN: Cytotoxic T lymphocytes patrol the body and screen cells for abnormalities. The CTLs SECRETE perforins in tightly enclosed SPACE between cells that leads to the formation of transmembrane channels through which the granzymes enter the cells and DIRECT them to apoptosis.

The correct CHOICE is (a) DIES by apoptosis

To elaborate: After the clearance of foreign ANTIGEN, the expanded T-cell population dies by apoptosis and a SMALL population of memory T-cells remains for future contact with the same antigen.

Correct choice is (d) Edward JENNER

Easy explanation: In 1796, Edward Jenner discovered the vaccine against smallpox by deliberately infecting an eight-year-old boy with cowpox and then injecting the pus of smallpox LESION under his skin. He then FOUND out that the boy showed immunity against the LATTER.

The CORRECT answer is (c) major histocompatibility complex

Explanation: Fragments of antigens are HELD at the surfaces of antigen presenting cells (APCs) with the help of MHC (major histocompatibility complex) MOLECULES. The T LYMPHOCYTES are activated with the help of antigen presenting cells.

The correct ANSWER is (a) hematopoietic stem cells

The BEST explanation: B and T cells arise from the same precursor – hematopoietic stem cells that undergo different pathways of differentiation. B-lymphocytes target the extracellular pathogens whereas the T-lymphocytes ATTACK intracellular pathogens.

The correct option is (a) lymph nodes

To EXPLAIN: When a FRAGMENT of ANTIGEN binds to the T-cell receptor, it results in the proliferation of a particular clone of T-cells. A T-cell can proliferate 3 to 4 TIMES per day, accompanied by enlargement of the lymph nodes.

Right choice is (c) CD4

To explain: The helper T CELLS have CD4 proteins on their surface INSTEAD of CD8 proteins as in case of cytotoxic T cells. Helper T cells play a role in orchestrating ATTACK against a specific pathogen.

The correct option is (a) HEAVY chain

Easy explanation: The class-switching of antibodies can TAKE place by CHANGING the heavy chains of immunoglobulins without make any CHANGE to the antigen binding region. B cells can change the antibodies they make even after PRODUCING them.

Correct option is (a) TOLL

The explanation is: The protein Toll, present in the FRUIT FLY, plays a DUAL role of promoting DORSOVENTRAL development of the embryo and providing the fly with immunity against pathogens.

Right OPTION is (d) FRANK MacFarlane Burnet

The best I can explain: Frank MacFarlane Burnet was an Australian immunologist who in 1957 proposed the clonal selection theory – a MODEL that dictates how the PRODUCTION of a single type of antibody is produced in excess.

Right CHOICE is (a) epitope

The explanation is: The ANTIGENIC DETERMINANT – epitome is the combining SITE of an antibody that has a complementary stereochemical structure to a particular portion of the antigen. Different ANTIBODIES contain variable epitopes.

Correct option is (a) virus

Easy EXPLANATION: The viruses (both DNA and RNA) always reside INSIDE the host CELL and hence can be classified as intracellular pathogens. Others such as bacteria can be intracellular or extracellular.

Correct answer is (a) Ralph Steinman

To explain I would say: The vital antigen PRESENTING cells (APCs) INCLUDE DENDRITIC cells and MACROPHAGES. Dendritic cells were discovered and characterized by Ralph Steinman of the ROCKEFELLER University in 1970s.

The correct answer is (C) AUTOANTIBODIES

The best explanation: For the body to DEVELOP immunologic tolerance, the production of autoantibodies MUST be prevented. Autoantibodies can react with the body’s own tissues and cause organ destruction.

The correct choice is (B) False

Explanation: UNLIKE B-lymphocytes, the T-cells do not secrete antibodies for DESTROYING the infected cells. The T-cells POSSESS T-cell receptors on their surfaces, by which they can interact DIRECTLY with the antigen-presenting cells.

The correct answer is (a) Helper T cells

Easiest explanation: Helper T cells (TH) play an important role in the attack against specific antigens. The HIV ATTACKS helper T cells which are necessary for the DIFFERENTIATION of B cells into antibody secreting plasma cells. When the count of TH cells in the body DROPS below 200 cells/μl the body becomes prone to infections.

Right option is (a) plasma cells

For explanation I would say: The antibody-producing B-cells are ACTIVATED after ENCOUNTER with ANTIGEN. A proportion of these antibody producing cells are differentiated into short-lived plasma cells that secrete large AMOUNTS of antibodies.

The correct ANSWER is (c) ALDARA

The EXPLANATION: The drug Imiquimod commercially known as Aldara is a drug that acts by activating the toll-like receptors at the site. This further allows MOUNTING of IMMUNE response at the site of application.

Correct option is (a) True

Best explanation: B lymphocytes play VITAL role in acquired immunity against diseases and antigens. Upon contact with an antigen, the B CELLS convert to plasma cells, the latter are found mainly in the bone marrow which is the soft tissue inside the bones.

Correct option is (b) 2, 2

To EXPLAIN: An antibody or immunoglobulin UNIT consists of four protein chains. Two identical Heavy chains and Light chains joined USING a disulphide bridge.

Correct choice is (b) IgM

The BEST I can explain: B cells produce FIVE different types of Immunoglobulins (ANTIBODIES) – IgG, IgM, IgA, IgD, IgE. The first antibody to be SECRETED by the B cells FOLLOWING stimulation by an antigen is IgM.

Right choice is (a) IgM

To explain I WOULD say: Binding of HEAVY chain of IgM LEADS to the activation of complement system that initiates the lysis of bacterial cells to which the antibody is bound. Similarly, binding of heavy chain of IGE initiates the ALLERGIC responses.

The correct option is (B) PROTEINS

The explanation: Cytokines are small proteins that work at low concentrations; secreted by a wide variety of CELLS and include interferons (IFs), interleukins (ILs), and tumor necrosis factors (TNFs). In addition to cell-cell contact, the T-cells also MEDIATE their interactions by cytokines.

The correct choice is (a) progenitor cells

For explanation: B-cells arise from UNDIFFERENTIATED and uncommitted progenitor cells. As the B-cells become mature they become committed TOWARDS PRODUCING a single type of ANTIBODY.

Correct option is (a) True

Explanation: Against EVERY antigen and associated DISEASE, an array of ANTIBODIES is generated. According to an earlier model – the “instructive model” the antigen instructs the lymphocytes to produce antibodies against itself.

The correct answer is (d) J-segment

Easy explanation: The small portion of the chromosome 2 that encodes for V region (VARIABLE region of the immunoglobulin) is called the J segment. On the CHROMOSOMES, the GENES encoding for variable and constant regions of the chromosomes are segregated.

The correct option is (C) FOXP3

The explanation: Regulatory T lymphocytes are inhibitory cells that suppress PROLIFERATION of immune cells. They possess CD4^+ and CD25^+ markers on their surface. The proliferation of TReg cells require a TRANSCRIPTION FACTOR FOXP3.

Correct choice is (d) CASPASES

Best explanation: After ENTERING the target cells through the perforin TRANSMEMBRANE channels, the GRANZYMES (PROTEOLYTIC enzymes) activate caspases that direct the cells to undergo apotosis.

Correct option is (b) DISULFIDE bonds

For explanation I would say: The ANTIBODIES are globular proteins that CONTAIN heavy CHAINS (molecular mass of 50,000 to 70,000 daltons) and LIGHT chains (23,000 daltons). The heavy and light chains are joined together by disulfide bonds.

Correct OPTION is (b) thymus-independent

To elaborate: T-cells are usually involved in the process of activation of B-cells and subsequent production of a SINGLE type of ANTIBODY. Few antigens such as polysaccharides of BACTERIAL cell walls do not REQUIRE the involvement of T-cells and therefore termed thymus-independent antigens.

Correct choice is (a) antibodies

To elaborate: Antibodies are proteins PRODUCED by the B lymphocytes and their DESCENDANTS (plasma cells) that are INCORPORATED in the plasma membranes of the former. The antibodies act as ANTIGEN receptors on the SURFACE of B cells.

The correct choice is (B) IGE

To EXPLAIN I would say: IgE is produced at high levels in response to parasitic infections and these immunoglobulins also BIND to the surface of mast cells with high affinity, TRIGGERING histamine release, which causes allergy and inflammation.