Structure and Function of Immune System Dr.Ghada Boghdadi

1. Structure and Function of Immune System Dr.Ghada Boghdadi

2. Objectives: • * Enlist the cells and organs of the immune system • * Describe the structure and function of cells and organs of the immune system • * Discuss the role of T-cell receptors and MHC molecules in the functioning of T cells • * Describe the roles of cytotoxic T cells, T-helper cells, and T-suppressor cells in specific immunity • Anantha Narayanan • Ch 15

3. Immunology: • study of our protection from foreign macromolecules or invading organisms and  our responses to them. Invaders own own proteins cells Immunity Autoimmunity Tumor

5. Characters of Adaptive Immunity: • Diversity • Memory • Specificity • *The immune system interact with one another by a variety • of signal molecules so that a coordinated response may be mounted.

6. There are two main lineages that derive from the hemopoietic stem cell:

7. Origin of Immune System Cells :

8. The human lymphoid system: • primary organs: bone marrow (in the hollow center of bones) and the thymus gland (located behind the breastbone above the heart) • secondary organs at or near possible portals of entry for pathogens: adenoids, tonsils, spleen (located at the upper left of the abdomen), lymph nodes (along the lymphatic vessels with concentrations in the neck, armpits, abdomen, and groin), Peyer's patches (within the intestines), and the appendix.

10. Immune System Cells: Cells of the innate immune system 1- NK 2- Phagocytic cells ( Monocytes/Macrophages) Cells that link the innate and adaptive immune systems Antigen presenting cells (APCs) 1- Monocytes/Macrophages 2- Dendritic cells Cells of the adaptive immune system 1- T lymphocytes 2- B lymphocytes

11. Lymphocytes: Originate from stem cells in bone marrow. Specialize into B cells (in the bone marrow) and T cells (in the thymus). After exposure to antigen, B cells differentiate into plasma cells whose primary function is the production of antibodies.  Similarly, T cells can differentiate into either T cytotoxic (Tc) or T helper (Th) cells of which there are two types Th1 and Th2 cells.

12. T Cell Development:

13. T-cells: There are functional subsets for T-cells • T-helper cells (CD4+) recognize Ags displayed on MHC II Th1 (cellular immunity) Th2 (humoral immunity) • T-cytotoxic (CD8+) recognize Ags displayed on MHC I • T-suppressor (Regulatory T-cells)

14. Main distinguishing markers of T and B cells

15. Clonal selection of Lymphocytes

16. Recognition of antigen by B cells:

17. Recognition of antigen by T cells:

18. Class II MHC Class I MHC Antigen TCR Antigen Presenting cell TCR Virus Infected Cell Helper T cell Cytotoxic T cell CD4 Protein CD8 Protein InterAction between Immune cells

19. Signals of Immune cells Interaction

20. NK cells * large granular lymphocytes * They unlike cytotoxic T cells, do not need to recognize a specific antigen before swinging into action. * Do not express: TCR Pan T marker CD3 Pan B marker SIg

21. Phagocytosis of microbes by Macrophages Or Dendritic cells Acquired immunity Innate immunity Present antigens to CD4-positive Th cells Destroy Microbes and secrete cytokines

22. Granulocytes Eosinophil Antiparasitic Neutrophil PMN Phagocytic Basophil Protection of mucosal surface (allergic reaction)

23. Activated Tc cell MO Microorganism IL-12 Naïve Helper T cell IL-12 pathway IL-4 pathway Th-1 Cell Th-2 cell IFN- IL-12 IL-4 IL-5 Plasma cell B cell Activated MO Antibody-mediated Immunity Cell-Mediated Immunity