BLOOD AND BODY DEFENCE Dr. Amel Eassawi Dr. Abdelrahman Mustafa 1

HMIM 224 L7: IMMUNITY 2

OBJECTIVES The student should be able to:  Discuss general overview of the immune system.  Differentiate between innate and adaptive immunity.  Identify the component of innate and adaptive immunity.  Define the term antigen, antibody and hapten.  Phases of immune response. 3

IMMUNITY Body’s ability to resist or eliminate potentially harmful foreign materials or abnormal cells. Immune system activities –Defends against invading pathogens. –Removes “worn-out” cells and tissue damaged by trauma. Immune surveillance. –Identifies and destroys abnormal or mutant cells that have originated in the body. –Removes inappropriate immune responses that can lead either to allergies or to autoimmune diseases. 4

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INNATE IMMUNITY Innate/Non-specific/Natural Immunity: –Nonspecific –Immediate response when body is exposed to threatening agent –Non-selective defend against foreign invaders –First line of defense –Rapid but limited responses 6

INNATE IMMUNITY Innate immunity Include: 1. Barriers –Physical –Chemical 2. Defensive cells –WBCs –Macrophages –Natural killer cells (NK) 3. Chemical defenses –Complement system 7

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INNATE IMMUNITY Inflammation: Biological response of vascular tissues to harmful stimuli. Interferon: Are named after their ability to "interfere" with viral replication. Complement system: Helps or “complements” the ability of antibodies and phagocytic cells to clear pathogens from an organism. 9

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LINES OF DEFENSE RESPONSE TO INFLAMMATION First line of defense: Tissue macrophages and physical barriers Second line of defense: Neutrophil Invasion of the inflamed area Third line of defense: Monocytes (macrophage) invasion of inflamed area Fourth line of defense: Increased production of granulocytes and monocytes by bone marrow 11

FORMATION OF PUS  Dead Neutrophils  Dead Macrophages  Necrotic tissue 12

1.Diapedesis 2.Chemotaxis 3.Opsonization 4.Degranulation 5.Phagocytosis & Digestion DEFENSIVE PROPERTIES OF MACROPHAGES AND NEUTROPHILS 13

INTERFERON α, β, and γ interferon. Released by virus infected cells. Function by blocking viral reproduction. 14

Mechanism of Action of Interferon in Preventing Viral Replication 15

COMPLEMENT SYSTEM Series of ~ 20 proteins The complement system, a group of inactive plasma proteins that, when sequentially activated by exposure to microorganisms, bring about destruction of foreign cells by attacking their plasma membranes. 16

ADAPTIVE IMMUNITY Adaptive or Acquired immunity –Specifically targets foreign material to which body has already been exposed –Body has taken time to prepare to attack –Ultimate weapon against most pathogens –Responses are mediated by β and T lymphocytes –Formation of memory cells allows system to react more quickly against specific invaders in the future 17

ADAPTIVE IMMUNITY Two types: 1.Active immunity – direct encounter with the antigen. 2.Passive immunity – without encounter with the antigen  Antibodies transferred from mother to the fetus.  Immunization by injecting antibodies 18

ADAPTIVE IMMUNITY Active immunity –“ self-generated” –Results from exposure to an antigen. –Cell mediated immunity (T cell immunity). –Antibody mediated immunity (humoral/ B cell immunity). Passive immunity –“borrowed immunity” –Results from transfer of preformed antibodies –Can provide immediate protection –Example of passive immunity is transfer of IgG antibodies from mother to fetus –Tetanus toxins, anti snake venom, rabies virus 19

ADAPTIVE IMMUNITY Antigen – Any substance when introduced into the body stimulates the production of an antibody. –Bacteria, fungus, parasite –Viral particles –Other foreign material Pathogen – An Antigen which causes disease. Hapten – Is not antigenic by itself. When combines with protein it become an antigen 20

ADAPTIVE IMMUNITY Antibody – A Y-shaped protein, found on the surface of B-Cells or free in the blood, that neutralize antigen by binding specifically to it. Also known as an Immunoglobulin Antigen 21

Origins of B and T lymphocytes After early childhood most new lymphocytes are derived from peripheral lymphocyte colonies rather than from bone marrow 22

B AND T LYMPHOCYTES Mainly produced from lymphoid colonies in lymphoid tissues Lymphoid tissues –Tissues that produce, store, or process lymphocytes –Include Bone marrow Lymph nodes Spleen Thymus Tonsils Adenoids Appendix Peyer’s patches (GAIT) 23

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Bone Marrow Pre-B Cell Pre-T Cell T-Cell T-supressor T4-helper B-Cell Plasma Cell IgG IgA IgM IgD IgE Interactions between T- and B-Cells T8-ctotoxic T- memory Cell B- memory Cell 26

PHASES OF IMMUNE MECHANISM Initial phase –Entry of antigen and its contact with the specific receptor on lymphocytic membrane. Central phase –Cooperation among different subset of lymphocytes that proliferate and differentiate to form T & B lymphocyte + memory cells Effector phase –Inactivation of antigen by sensitized T & B lymphocytes 27

PRIVILEGED IMMUNITY The uterus is an "immunologically privileged" site where immune responses are subdued. The placenta functions as an immunological barrier between the mother and the fetus, The placental trophoblast cells do not express the classical MHC class I (major histocompatibility class I). 28

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REFERENCES  Human Physiology, Lauralee Sherwood, seventh edition.  Text book Physiology by Guyton &Hall,11 th edition.  Text book of Physiology by Linda S. Contanzo, third edition.  Physiology by Berne and Levy, sixth edition. 30