1. Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India

2. © 2008, YCMOU. All Rights Reserved.2 OC-SBT091-CP1-01 Introduction Programmes and Courses SEP–SBT091–CP1-UN-01

3. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.3 Credits  Academic Inputs by Arun Punaji More. M.Sc. (Microbiology) ‏ Experience: 11 Years arunmesh@hotmail.com

4. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

5. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Describe the structures of immunoglobulin molecules. Describe the functions of immunoglobulin molecules.

6. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.6 Introduction  All vertebrates secrete special molecules which protect them from pathogenic microorganism and their toxic effects; these molecules are known as immunoglobulins.  Immunoglobulins are secreted by specialized cells called as plasma cells of immune system.  To understand how the immune system protect the vertebrates from pathogenic microorganisms and their toxic effects it is necessary to understand the structure and functions of immunoglobulins.

7. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.7 Structure of Immunoglobulins-1  Immunoglobulins are proteins secreted by plasma cells derived from B lymphocytes.  A single immunoglobulin molecule is made of with four polypeptide chains; two of them are small and two of them are large.  The small polypeptide chains are called as light chains whereas the larger polypeptide chains are called as heavy chains.  The two light chains in a single immunoglobulin molecules is identical to each other.

8. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.8 Structure of Immunoglobulins-2  The two heavy chain in a given immunoglobulin molecule are identical to each other.  There are two types of light chains: kappa( κ ) and lambda( λ).  Since a given immunoglobulin molecule the light chains are identical, they are of the same type i.e. the given immunoglobulin molecule possess either kappa or lambda chains.  The light chains are associated with the heavy chains at their N-terminal ends by disulfide bonds.

9. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.9 Structure of Immunoglobulin-3 Arrangement of heavy and light chains of Ig The two light and two heavy Chains are arranged in letter Y Shaped in the immunoglobulin molecule. These chains are held together by Disulfide bonds as shown in this figure

10. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.10 Structure of Immunoglobulins-4 Fine structure of antibody molecule:- Globular structure of polypeptide Chains of antibody molecule. Two light chains are identical to each other. Two heavy chains are identical to each other.

11. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.11 Structure of Immunoglobulins-5  The treatment of basic immunoglobulin molecule with enzyme papain produces three fragmants of the molecules; two of these are identical and are referred to as Fab fragments (Fragment, antigen binding) having molecular weight of 45000 where as the third comparatively large fragment is referred to as Fc fragment( Fragment, crystalizable) having molecular weight of 50000.  The Fc fragment is associated with number of biological activities whereas the Fc fragment is associated with antigen binding activities.

12. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.12 Structure of Immunoglobulins-6  Treatment with enzyme pepsin generate a single large fragment of molecular weight of 100000 consist of two Fab portions.  The treatment of antibody molecule with mercaptoethanol generate four polypeptide chains: two light chains and two heavy chains.  The molecular weight of light chain is 25000.  The molecular weight of heavy chain is 50000.  Thus the molecular weight of complete antibody molecule is 150000 MW.

13. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.13 Structure of Immunoglobulins-7  Structure of light chains:- Each light polypeptide chain is made of with approximately 220 amino acids. The approximate mass of light chain is 25,000 Da. The light chains of immunoglobulin molecule is made of with polypeptide chains with similar globular structures; these are called as globular subunits or domains. Each domain consist of approximately 110 amino acids forming polypeptide portion folded into two layers of β -pleated sheets which are held together with intrachain disulphide bond (disulphide bridge).

14. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.14 Structure of Immunoglobulins-8  Structure of light chain:- The amino acids sequences of domains of light and heavy chains show marked similarity except the amino terminal of light chains which show variations in this sequence when compared with the amino acid sequences of other domains in the molecule. The hypervariable region of light chain is complementarity-determining region since it determine the antigen specificity of immunoglobulin molecule. The other domain of light and heavy chains which show marked similarity are called as constant regions or constant domains.

15. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.15 Structure of Immunoglobulins-9  Structure of heavy chains:- Each heavy chain is made of with approximately 440 amino acids. The mass of heavy chain is approximately 50,000 to 70,000 Da. The loop of polypeptide forming domains are in form of β sheet held together by a single disulphide bond. The amino acid sequence of the constant domains of heavy chain determine the classes of heavy chain.

16. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.16 Structure of Immunoglobulins-10  Structure of heavy chains:- In human there are five classes of heavy chain as : gamma(γ), alpha(α), mu(μ), delta(δ) and epsilon(ε). The type of heavy chain determine the class of immunoglobulin. Immunoglobulin molecules of same class showing variations in heavy chains are termed as isotypes of immunoglobulin. There are five isotypes corresponding to five classes of immunoglobulin molecules.

17. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.17 Structure of Immunoglobulins-11 Action of pepsin:-

18. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.18 Structure of Immunoglobulins-12 Action of papain:-

19. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.19 Structure of Immunoglobulins-13 Biological functions of various domains of antibody:-

20. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.20 What We Learn…..  Structure of immunoglobulin molecules  Characteristics of immunoglobulin molecules

21. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.21 Critical Thinking Question  Why a antibody molecules possess antigen sites of the identical specificity?

22. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.22 Hints For Critical Thinking Question  Types of polypeptide chains of a antibody

23. School of Science and Technology, Online Counseling Resource… © 2008, YCMOU. All Rights Reserved.23 Study Tips  Book Title: Immunology Title: Immunology Author: Author: Richard A. Goldsby, Thomas Kindt, Barbara A. Osborne. Publication: Publication: W.H. Freeman and Company, New York.

24. © 2008, YCMOU. All Rights Reserved.24 End of the Presentation Thank You !