Model Answer: LBTC601: Immunology (Int. UG/PG Biotechnology VI sem)

1 Naveen Kumar Vishvakarma

Model answers Integrated UG/PG Biotechnology VI semester Examination 2013-2014

LBTC 601 : IMMUNOLOGY Section A. 1. Choose one correct option for the following questions: S.N. Correct Option S.N. Correct Option

(i). a E. Metchikov (vi). d Human immunodeficiency virus (ii). d Agents of active immunization (vii). d Toll-like receptor

(iii). b Rosalyn Yalow (viii). c B7 (iv). b Heavy chain (ix). b 2 (v). a Myasthenia Gravis (x). b Transporter associated with antigen processing

Section B:

2. How cells of immune system generated? Write a flow diagram for hematopoiesis. Discuss differences between B lymphocyte and T Lymphocytes. Cells of immune system are generated through process of hematopoiesis. This can be divided in to two wings namely Lymphopoiesis and myelopoiesis. Discussion about hematopoietic stem cells, self renewal of HSCs and commitment by progenitors are necessary.

Difference between B and T lymphocyte: Differences in generation/maturation, cell surface markers, profile of secreted molecules, antibody production and participation in Humoral/CMI must discussed.

Model Answer: LBTC601: Immunology (Int. UG/PG Biotechnology VI sem)

2 Naveen Kumar Vishvakarma

3. What are polyclonal and monoclonal antibodies? Briefly describe process for production of monoclonal antibodies along with their application? Polyclonal antibody: A mixture of antibodies produced by a variety of B-cell clones that have recognized the same antigen. Although all of the antibodies react with the immunizing antigen, they differ from each other in amino acid sequence. Monoclonal antibody: Homogeneous preparation of antibody molecules, produced by a single clone of B lineage cells, often a Hybridoma, all of which have the same antigenic specificity. Generation of polyclonal antibodies through encounter with single antigen must be discussed. Production process for monoclonal antibodies: Monoclonal antibodies are produced through Hybridoma technology and Nobel Prize was awarded for devising such protocol to Cesar Milstein and George Kohler along with Neils Jerne (also in the field of immunology). This technology utilizes fusion of myeloma cancerous cells with single clones of Plasma cells.

Discussion about genetic makeup of myeloma cells and antibody producing B lymphocytes and selection through HAT medium are necessary. Monoclonal antibodies are used in clinical as well as research and development. Clinical use includes diagnostic, imaging, and therapeutics. Discussion about radio-labeled, Fluorescent antibodies, Immunotoxins is required.

Model Answer: LBTC601: Immunology (Int. UG/PG Biotechnology VI sem)

3 Naveen Kumar Vishvakarma

4. With appropriate diagram, describe antigen presentation and interaction of MHC-antigenic peptide

complex-TCR.

Description about endogenous (Cytosolic) and exogenous (endocytic) pathways, MHC class I and II along with TAP, HLA DM CLIP, Invariant chain is required.

Brief description about components of TCR and co-recognition of MHC I and II molecule by CD8 and CD4 must be included in answer. Additionally, Strengthening of MHC-peptide-TCR interaction with help of adhesion molecules also required.

Model Answer: LBTC601: Immunology (Int. UG/PG Biotechnology VI sem)

4 Naveen Kumar Vishvakarma

5. With help of appropriate diagram, describe regulation of complement activation?

Regulation of complement activation before and after convertase assembly must be discussed separately. A brief description about molecules involved in complement regulation (Factor 1, Factor H, C1Inh, C4bBP, CRI, CR2 MCP, DAF, s protein, HRF and MIRL) is required.

Model Answer: LBTC601: Immunology (Int. UG/PG Biotechnology VI sem)

5 Naveen Kumar Vishvakarma

6. What do you understand with hypersensitivity? What are their types? Briefly describe Allergy.

Hypersensitivity Exaggerated immune response that causes damage to the individual. Immediate hypersensitivity (types I, II, and III) is mediated by antibody or immune complexes, and delayed-type hypersensitivity (type IV) is mediated by TH cells. P. G. H. Gell and R. R. A. Coombs proposed a classification scheme in which hypersensitive reactions are divided into four types. Three types of hypersensitivity occur within the humoral branch and are mediated by antibody or antigen-antibody complexes: IgE-mediated (type I), antibody-mediated (type II), and immune complex–mediated (type III). A fourth type of hypersensitivity depends on reactions within the cell-mediated branch, and is termed delayed-type hypersensitivity, or DTH (type IV). Each type involves distinct mechanisms, cells, and mediator molecules. This classification scheme has served an important function in identifying the mechanistic differences among various hypersensitive reactions, but it is important to point out that secondary effects blur the boundaries between the four categories.

Description about allergen-mediated cross-linking of reagenic IgE antibody, degranulation and effect on target cell type or organ is necessary.

7. Write short note on following:

a) Macrophages Macrophages are mononuclear phagocytes and have ability of antigen presentation on class II MHC molecules. HSC are first differentiated into monocytes. Monocytes circulate in the bloodstream for about 8 h, during which they enlarge; they then migrate into the tissues and differentiate into specific tissue macrophages or, as discussed later, into dendritic cells. Differentiation of a monocyte into a tissue macrophage involves a number of changes: The cell enlarges five- to tenfold; its intracellular organelles increase in both number and complexity; and it acquires increased phagocytic ability, produces higher levels of hydrolytic enzymes, and begins to secrete a variety of soluble factors. Macrophages are dispersed throughout the body. Some take up residence in particular tissues, becoming fixed macrophages, whereas others remain motile and are called free, or wandering, macrophages. Free macrophages travel by amoeboid movement throughout the tissues. Macrophage-like cells serve different functions in different tissues and are named according to their tissue location:

Model Answer: LBTC601: Immunology (Int. UG/PG Biotechnology VI sem)

6 Naveen Kumar Vishvakarma

Alveolar macrophages in the lung Histiocytes in connective tissues Kupffer cells in the liver Mesangial cells in the kidney Microglial cells in the brain Osteoclasts in bone

Brief Discussion about

Opsonization Phagocytosis, Oxygen-dependent and –independent killing MHC II expression

Model Answer: LBTC601: Immunology (Int. UG/PG Biotechnology VI sem)

7 Naveen Kumar Vishvakarma

b) Cytokines The development of an effective immune response involves lymphoid cells, inflammatory cells, and hematopoietic cells. The complex interactions among these cells are mediated by a group of proteins collectively designated cytokines to denote their role in cell-to-cell communication. Cytokines are low-molecular weight regulatory proteins or glycol proteins secreted by white blood cells and various other cells in the body in response to a number of stimuli. These proteins assist in regulating the development of immune effector cells, and some cytokines possess direct effector functions of their own. Brief discussion about Lmphokine, Monokine, chemokines, interleukins; Autocrine, paracrine, endocrine nature, Pleiotropy, Redundancy, Synergy, Antagonism, Cascade induction are required.

Model Answer: LBTC601: Immunology (Int. UG/PG Biotechnology VI sem)

8 Naveen Kumar Vishvakarma

8. Briefly describe about Receptor editing and Affinity maturation. Receptor editing: Receptor editing is phenomenon implicated by self reactive B cells to avoid deletion through negative selection. Once, a cell clone is identified to have self reactive BCR, maturation of that cell ceases, before subsequent induction of apoptosis for clonal deletion. Maturation of the self-reactive cell is arrested while the B cell “edits” the light-chain gene of its receptor. Self-reactive B-cells bind a self-antigen, maturation is arrested; the cells up-regulate RAG-1 and RAG-2 expression and begin further rearrangement of their endogenous light-chain DNA. Some of these cells succeed in replacing the light chain of the self antigen reactive antibody with a chain encoded by endogenous -chain gene segments. As a result, these cells will begin to express an “edited” mIgM with a different light chain and a specificity that is not self-reactive. These cells escape negative selection and leave the bone marrow. Elaborated description required. Affinity maturation The average affinity of the antibodies produced during the course of the humoral response increases remarkably during the process of affinity maturation, an effect first noticed by H. N. Eisen and G.W. Siskind when they immunized rabbits with the hapten-carrier complex DNP-BGG. The affinity of the serum anti-DNP antibodies produced in response to the antigen was then measured at 2, 5, and 8 weeks after immunization. The average affinity of the anti-DNP antibodies increased about 140-fold from 2 weeks to 8 weeks. Subsequent work has shown that affinity maturation is mainly the result of somatic hypermutation. Description about affinity maturation-mediated production of antibodies during secondary response against any antigen is required.