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Introduction to Medical Immunology (1)

Mar 06, 2015

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ASSESSMENT Continuous assessment: Quizzes 10% Mid Semester Exam 30% Final Semester Exam 60%

Team Teaching Prof Dr Zauyah Yusuf Madam Mahani Mahadi Madam Shamima Abdul Rahman

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SynopsisBasic immunology includes topics and themes considered essential for basic understanding of immune system. It covers the structure, organization and function of the immune system together with the mechanism of normal immune response. The immunopathology of diseases caused by an abnormal immune response and the basis of immunological tests used in the diagnosis of certain diseases are also introduced.chapter 1 4

References Mark P, Diego V. 2009. Basic and Clinical Immunology. Second Edition. Elsevier Churchill Livingstone. Roderick N and Matthew H. 2004. Immunology for Medical Students. Elsevier Mosby. Stites DP, Terr Al and Parslow TG. 2001. Medical Immunology. 10th Edition, Appleton & Lange, Prenticehall International Inc. http://www.microbiologybytes.com/iandi/2b.html http://www.wellesley.edu/Biology/Concepts/Html/anti body.html http://faculty.ccbcmd.edu/courses/bio141/lecguide/un it5/index.html#abystructurechapter 1 5

Introduction to Immune SystemPn Mahani Mahadichapter 1 6

Learning Outcomes: At the end of this lecture, student should be able to : Identify and differentiate cells of immune system Identify tissues of immune system Explain roles of each cells and tissues of immune system.

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What is immunology?

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Immunity or latin words immunis mean free from burden or defined as a resistance to disease caused any microorganism. Immune system is a collection of cells, tissues and molecules that mediate resistance to infections. Immunology is the study of the immune system and its responses to invading pathogens.

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Role of The Immune System: 1. Defense against infections 2. Recognizes and responses to tissue grafts and newly introduced proteins 3. Defense against tumors 4. Produce antibodies ( highly specific reagents for detecting any class of molecules)chapter 1 10

Types of Immunity?known as natural or native immunity. is a initial protection against infections and Block the entry of microbes

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known as specific or acquired immunity. develops more slow & mediates the later, more effective against infection. stimulated by microbe that invade tissue.

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Cells of Immune System Bone marrow is the source of the precursor cell that give rise to the cellular constituent of immune system. Production of immune cells or all blood cells lineage is known as haemopoiesis process.

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Immunology concentrates upon the roles of white blood cells in host defense included granulocytes : (neutrophils, eosinophils and basophils), monocytes and dendritic cells and lymphocytes.

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* Granulocytes (BEN) Appr 65% of all white cells Contain granules in their cytoplasm Circulate in blood and are involved in inflammatory responses. Mast cell share common features with basophil but unidentified precursor.

MonocytesAppr between 5 to 10% of circulating white cells. Short half life (24 hrs in the blood).chapter 1 14

MonocytesWhen they enter extravascular pool and become resident in the tissues known as macrophages MQ (mature form of monocytes) They are larger than neutrophil and lymphocytes, have a single nucleus and abundant granular cytoplasm. Special MQ exists in different tissues- Kupffer cells (liver), mesangial cells (kidney), microglial cells (brain) and osteoclast (bone). Dendritic cells -> very small population , derived from bone marrow and specialized function in activation and priming of lymphocytes.chapter 1 15

Lymphocytes25-35% of white cells Has 2 subtypes: B and T, present in blood with 1:5 ratio. Found in the blood, lymphoid organ or tissues and sites of inflammation and Arise from bone marrow.

Natural killer cellsmall population, capable of lysing virus infected cells and tumour cells, natural. Came from thymus.chapter 1 16

LymphocytesB lymphocytes differentiate in bone marrow b4 released into the circulation. Role as recognition of macromolecules (antigen) thro surface receptors (antibody). May mature into plasma cells remain fixed in the tissues and acts as secretors of soluble antibody. T lymphocytes derived from thymus, pivotal cell in immune response, able to recognize and destroy infectious agents and foreign tissues.chapter 1 17

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Tissues and Organ of Immune System

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The tissues of immune system consist of the generative ( primary) lymphoid organs in which B and T lymphocytes mature and become competent and peripheral (secondary) lymphoid organs which adaptive immune response are initiated. Primary lymphoid organs composed of thymus and bone marrow. Sites of development and maturation of immune response cells.chapter 1 20

Tissues and Organ of Immune SystemPrimary Lymphoid OrganBone marrow

Secondary Lymphoid OrganLymph nodes Spleen MALT

Thymus GALTchapter 1 21

The bone marrow and the thymus constitute the primary lymphoid organs. Both B-lymphocytes and T-lymphocytes are produced from stem cells in the bone marrow. Blymphocytes mature in the bone marrow while Tlymphocytes migrate to the thymus and mature there. After maturation, both B-lymphocytes and Tlymphocytes circulate through and accumulate in secondary lymphoid organs.

1) Bone Marrow: All immune cells derived from stem cell in the bone marrow. Site of origin of red blood cells, white blood cells (immune cells) and platelet. 2) Thymus: Lymphoid cells undergo a process of maturation and education prior to release into the circulation. allows T cells to develop the important attribute known as self tolerance.chapter 1 23

Primary and Secondary Lymphoid organs

Thymus

grows rapidly during first year, then stays same size through adulthood. Decreases in size after 60 years. No reticular fibers: internal network formed by epithelial cells with long processes. Cortex (numerous lymphocytes) and medulla (fewer lymphocytes) Site of maturation of T cells: many T cells produced here, but most degenerate. Those that remain can react to foreign substances, but not to healthy body tissue.chapter 1 25

Secondary lymphoid organs.a) Which consist of the lymph nodes, the spleen, mucosa-associated (MALT) and gut-associated (GALT) lymphoid tissue. b) Have 3 major functions: 1. residence of variety of lymphoid cells, 2. traps for antigen, 3. anatomical site in which immune responses are initiated.

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Lymph Nodes Superficial (near skin) and deep. Organized into cortex and medulla with dense connective tissue capsule surrounding. Trabeculae extend within. Reticular fibers form supporting network. Only structures to filter lymph Afferent and efferent vessels Substances removed by phagocytosis or stimulate lymphocytes to proliferate in germinal centers. Cancer cells often migrate to lymph nodes, are trapped there, and proliferate. Can move from lymphatic system to circulatory system spreading cancer through body.chapter 1 27

3 Regions of Lymph NodesCortexoutermost layer- contains mostly B lymphocytes, plus both follicular dendritic cells and macrophages all arranged in clusters called primary follicles. Following antigenic stimulation the primary follicles become secondary follicles consisting of concentric rings of densely packed lymphocytes and central lymphocytes, macrophages, and dendritic cells. contain large proliferating B lymphocytes and plasma cells interspersed with macrophages and dendritic cells.chapter 1 28

Follicles

Germinal Centers

2) Spleen act as part of the immune system and as a filter. located in the upper left quadrant of the abdomen. two distinct components of the spleen, the red pulp and the white pulp. Red pulp: consists of large numbers of sinuses and sinusoids filled with blood 1)is responsible for the filtration function of the spleen. 2)facilitate removal of old or damaged red blood cells from the circulation.chapter 1 30

White pulp consists of aggregates of lymphoid tissue and is responsible for the immunological function of the spleen contains T cells, B cells and accessory cells purpose is to mount an immunological response to antigens within the blood. Surrounds the splenic arteries, forming a periarteriolar lymphoid sheath (PALS) populated mainly by T lymphocytes. Clusters of B lymphocytes in the White Pulp form primary follicles occupying a more peripheral position. Upon antigenic challenge, these primary follicles develop into characteristic secondary follicles containing germinal centers.chapter 1 31

Functions of the SpleenThe immune functions include: y proliferation of lymphocytes y production of humoral antibodies y removal of macromolecular antigens from the blood The hematopoietic functions include: y formation of blood cells in fetal life y removal and destruction of senile, damaged and abnormal RBCs and platelets y retrieval of the iron from hemoglobin

Spleen

Spleen

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Mucosa-Associated (MALT) Lymphoid Tissue. lymphoid tissue is also found at other sites, mostly in the gastrointestinal tract, respiratory tract (tonsillar, naso-pharyngeal, bronchial) and urogenital tract. Gut-Associated (GALT) Lymphoid Tissue Peyer patches large aggregates of lymphoid tissue found in the small intestine. facilitate the generation of an immune response within the mucosa. Function similar to bone marrow.chapter 1 35

Lymphocyte Recirculation. Total number of lymphocytes in a healthy adult is about 1012 of which 0.1% are renewed daily. They do not reside in any single organ They re-circulate between the blood, tissues and lymphoid organ. Complete cycle of circulation in 1-2 days. It is a process of immune surveillance and controlled according to cell type and anatomy.chapter 1 36

Circulation - virgin lymphocytes move from the primary to secondary lymphoid tissue via the blood activated lymphocytes move from the spleen, lymph nodes and MALT into the blood and hence to other lymphoid and non-lymphoid tissues antigen presenting cells such as macrophages and dendritic cells may carry antigen back to lymphoid tissues from the periphery.chapter 1 37

Overview of the Lymphatic System

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Thank You

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