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

2. OC-SBT052-U01-03 Introduction Programmes and Courses  SEP – SBT052 – Unit 01

3. School of Science and Technology, Online Counseling Resource… © 2007, 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… © 2007, 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… © 2007, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Describe different cells of immune system and Describe functions of different cells of immune system

6. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.6 Introduction  This presentation is about Different types of T-Lymphocytes such T helper (Th) Lymphocytes. Th1 and Th2 Lymphocytes. Development and maturation of T Lymphocytes. Interaction of APC ( Antigen Presenting Cells) and T lymphocytes. Mechanisms of activation of T Lymphocytes

7. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.7 Cells of Immune System-1  Cells of lymphoreticular system work as cells of immune system.  These are of two types: 1. Structural Cells: 1. Reticulum cells. 2. Endothelial cells. 3. Fibroblast. 2. Immune Cells: 1. Lymphocytes. 2. Macrophages. 3. Plasma cells. 4. Mast cells.

8. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.8 Cells of Immune System-2 All immune cells originate from a hematopoietic stem cell in the bone marrow. The hematopoietic stem cell initially give rise to two major progenitor cell lineages: a myeloid progenitor cells and lymphoid progenitor cells. From myeloid progenitor cells differentiate different cells of immune system such as monocytes, dendritic cells, macrophages, megakaryocytes and granulocytes. From lymphoid cells differentiate T Lymphocytes, B Lymphocytes and Natural killer cells.

9. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.9 Cells of Immune System-3 Genesis Of Immune Cells is shown here in this diagram.

10. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.10 Cells of Immune System-4  Lymphocytes:  These are small, round and mobile cells of the immune system.  They are found in lymph and lymphoid organs such as lymph nodes, thymus and spleen.  Lymphocytes are of two types:  T-Lymphocytes and  B-Lymphocytes.  T- Lymphocytes get differentiated in the thymus.  B-lymphocytes mature in bone marrow.

11. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.11 Main Features of T Lymphocytes  Classes of T-Lymphocytes: Four classes of T-Lymphocytes are: Four classes of T-Lymphocytes are: 1.Helper T Lymphocytes. Th1 Lymphocytes. Th2 Lymphocytes 2.Suppressor T Lymphocytes. 3.Natural Killer T Lymphocytes. 4.Cytotoxic T Lymphocytes.

12. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.12 Maturation of T Lymphocytes-1 Main Features of Maturation of T-Lymphocytes are: T-Lymphocytes mature in thymus. T –Lymphocytes maturation is stimulated by Interleukin-7 produced by stromal cells of bone marrow. Maturation of T cells involve generation of large proportion of functional antigen receptors on these cells in Thymus. The generation of these antigen receptors on T cells is achieved by a process called as somatic recombination.

13. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.13 Maturation of T Lymphocytes-2  Main Features of Maturation of T Lymphocytes are:- In somatic recombination DNA sequences which encode for the different antigen receptors on the T cells and which are separated initially are brought together by enzymatic deletion of intervening sequences and religation. Thus the diversity of different antigen receptors generated by different permutations and combination of the genes encoding these antigen receptors as described above. After the maturation as mentioned above there is selection of non-self antigen recognizing T cells and elimination of self–antigen reacting T cells in Thymus.

14. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.14 Maturation of T Lymphocytes-3  Selection of Maturation of T Lymphocytes are:- There are two types of processes by which this selection of matured T Lymphocytes is achieved: Positive selection: In this there is selection of T lymphocytes whose receptors bind with MHC molecules with low avidity. And the t cells which can not recognize the self MHC molecules are removed by the process of apoptosis. Negative selection: In negative selection, those T-cells are eliminated whose antigen receptors react strongly with the self antigens.

15. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.15 Main Features of T Lymphocytes-4  Main Features of T Lymphocytes are:-  They initiate and regulate all types of immune responses in body.  They only recognize foreign antigens in association with the MHC molecules.  They possess CD2 surface antigen or marker on their surface.  CD2 marker distinguishes T-cells from B-cells.  They possess MHC class I molecules on their cells surface.  T Lymphocyte possess TCR (i.e. T Cells Receptor) on their cells surface which are monovalent.

16. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.16 Main Features of T Lymphocytes-5  Main Features of T Lymphocytes are:-  T cells receptors are membrane bound whereas the receptors on B cells also appears in soluble form.  On T cell membranes the T cells receptors are associated with signal transducing complex called as CD3.  T cells recognize the foreign antigen only when it is presented to it in association with the MHC molecules. This phenomenon is called as self-MHC- restriction.  T cells receptor are heterodiamer molecules of polypeptide chains of either alpha and beta or gamma or delta.

17. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.17 Activation of T-lymphocyte  Activation of T lymphocyte through the interaction between APC’ MHC class II molecule and T cell’s TCR molecule and also through the interaction between B7 of APC and CD28 of T cell.

18. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.18 Th1 Lymphocytes-1 Helper T Lymphocytes:- Th1 Lymphocytes: There are two subtypes of Th cells:  Th1 and  Th2 Lymphocytes. Th1 lymphocytes recognize foreign antigen +MHC class I complex expressed on the host cell surface. Th1 cells after recognizing foreign antigen on the infected cells’ surface release cytokines, IL-2 that activate infected cells to kill pathogens inside them.

19. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.19 Th1 Lymphocytes-2  Th1 Lymphocytes: Th1 cells produce IL-2 which induce T–cells proliferation. Th1 cells stimulate CD8+ cells (Cytotoxic cells) division and cytotoxicity. Th1 cells also produce interferon gamma which activate macrophages to kill intracellular pathogens such as mycobacteria, protozoa and fungi.

20. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.20 Th1 Lymphocytes-3  Th1 Lymphocytes:  E.g. macrophages infected with M.tuberculosis can not kill these bacteria normally, because M.tuberculosis prevent fusion of lysosomes with endosomes in which tubercle bacilli grow. But when Th1 cells activate this tubercle bacilli infected macrophage, fusion of lysosome and endosome take place killing tubercle bacilli.

21. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.21 Th1 Lymphocytes-4  Th1 Lymphocytes: Interferon gamma produced by the Th1 cells activate NK cells to cytotoxicity. Interferon gamma stimulated macrophages produce IL-12 which stimulate Th1 cells to produce interferon gamma. Over-amplification of Th1 responses lead to pathogenesis of autoimmune diseases such as rheumatoid arthritis and multiple sclerosis.

22. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.22 Th1 Lymphocytes-5  Development of Th1 Lymphocytes

23. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.23 Th2 Lymphocytes-1 Th2 Lymphocytes: Th-2 lymphocytes mainly induce humoral immune responses by stimulating B – lymphocytes to differentiate into antibody producing plasma cells. They are produced in helminthes infections. Th2 lymphocytes produced IL-4, IL-5, IL-6 and IL-10 cytokines. IL-4 induce class–switching of B lymphocytes to IgE producing B lymphocytes and suppression of Th-1 differentiation.

24. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.24 Th2 Lymphocytes-2  Th2 Lymphocytes: Role of Th-2 cells in activation of B cells to T-cell dependent antigen:-

25. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.25 Th2 Lymphocytes-3  Th2 Lymphocytes:  IL-5 promotes the growth of eosinophils.  They activate mast cells and eosinophils.  Th2 cells are activated by IL-4 cytokine.  Over-amplification of Th-2 responses lead to development of allergic diseases.

26. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.26 What We Learn…..  Different types of T lymphocytes.  Maturation of T lymphocytes.  Mechanisms of mounting immunological responses T lymphocytes.  Cytokines secreted by T lymphocytes and B lymphocytes.  T-cells-dependent antigens.  T-cells-independent antigens.

27. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.27 Critical Thinking Questions  Why A.I.D.S. patients become susceptible to all types of infections and cancers?

28. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.28 Tips for Critical Thinking Questions  Th cells crucial role in mounting different types of immunological responses.

29. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.29 Study Tips  Book Title:Immunology, 5 th ed. Title: Immunology, 5 th ed. Author:Richard A. Goldsby & Thomas J. Kindt, etc. Author: Richard A. Goldsby & Thomas J. Kindt, etc. Publication: Publication: W.H. Freeman and Company, New York.  Journal Article Title:Cytolytic pathways in Haematopoietic stem Transplantation. Title: Cytolytic pathways in Haematopoietic stem Transplantation. Author: Marcel R. M. van den Brink and Steven J. Burakoff. Author: Marcel R. M. van den Brink and Steven J. Burakoff. Publication: Publication: Nature review| Immunology,vol.2,April 2002.

30. End of the Presentation Thank You !