The IMMUNE SYSTEM

NORTHee 1965 City,. COLLEGE OF HEALTH AND SCIENCES UNIVERSITY OF NORTHERN PHILIPPINES TAMAG, VIGAN CITY 2700 ILOCOS SUR.

IMMUNE SYSTEM. Lymphatic system Computerized war machine CELLS OF THE IMMUNE SYSTEM 1. Myeloid Lineage 2. Lymphoid Lineage.

Major Functions of the Immune System: 1. Block harmful agents 2. Seek-out invasive pathogens 3. Isolate and neutralize activity of that antigen.

ACQUIRED IMMUNITY. type of resistance that is characterized by specificity for each individual pathogen the ability to remember a prior exposure (MEMORY) which results in an increased response upon repeated exposure..

ACQUIRED IMMUNITY. LYMPHOCYTES the key cell involved in adaptive immunity. Represents approximately 20% of the circulating WBCs. Has a large rounded nucleus which contains a dense nuclear chromatin.

ACQUIRED IMMUNITY. 2 MAJOR STAGES OF LYMPHOCYTE DEVELOPMENT Antigen Independent Stage of Lymphopoiesis Antigen Dependent Stage of Lymphopoiesis.

THE LYMPHOID SYSTEM. 1. Primary/Central Lymphoid Organs developmental sites a . Bone Marrow main source of hematopoietic stem cells Center for antigen-independent lymphopoiesis . b. Thymus small , flat bi-lobed organ found in thorax or chest cavity right below the thyroid gland and overlying the heart. • An endocrine gland • Cortex- where thymocytes can be found (85% of population of T cells) • Medulla - where mature T cells can be found. • Thymic stromal cells - include epithelial cells , macrophages and dendritic cells.

THE LYMPHOID SYSTEM. cea negatne cortex Ttymc eptreta æl (p«tve arc —at'.•e sucton) corücccretmary T en to perlßlery.

THE LYMPHOID SYSTEM. 2. Secondary/Peripheral Lymphoid Organs activation sites for lymphocytes A . Encapsulated Organs 1. Spleen - largest secondary lymphoid organ that is found on the ULQ of the abdomen just below the diaphragm.

THE LYMPHOID SYSTEM. Trabecular Gemiral fobck 1B cdls) Marenal Sinuses in red pup.

THE LYMPHOID SYSTEM. Main Types of Splenic Tissue: a. Red Pulp - involved in culling process, pitting AND platelet sequestration 1/3 PRODUCED PLATELETS - stored in spleen 2/3 CIRCULATING PLATELETS SPLENECTOMY - lead to increased platelet count.

THE LYMPHOID SYSTEM. b. White pulp - contains lymphoid tissue that is arranged around arterioles as PALS ( Periarteriolar Lymphoid Sheath) T cells - found near the central arteriole. Naïve B cells/ Virgin B-cells/Unstimulated/Inactivated B -cells - are found on primary follicles Activated B cells (Plasma Cell And Memory Cell) - are found on Secondary Follicles (germinal centers) Marginal zone contain macrophages.

THE LYMPHOID SYSTEM. SITES OF ENTRY OF LYMPHOCYTE/ANTIGEN INTO SPLEEN: a. Specialized Capillaries on marginal sinus b. Via trabecular artery.

THE LYMPHOID SYSTEM. 2. Lymph Nodes junctional filter of the lymphoid system . Sizes may range from 1mm to 25 mm . Cortex - B-cell area; also contains primary follicles which small amount of T cell and follicular dendritic cells and secondary follicles that contains germinal center. Paracortex - T-cell area Medulla- contains differentiated cells and APCs Axillary Lymph Nodes Inguinal Lymph Nodes Cervical Lymph Nodes.

THE LYMPHOID SYSTEM.

THE LYMPHOID SYSTEM. Lymphocyte traffic/recirculation movement of lymphocytes from blood to lymphoid organs and back to the blood. Site of Entry and Exit of Lymphocytes in the lymph node: Afferent Arteriole Efferent arteriole.

THE LYMPHOID SYSTEM. B . Non-encapsulated organs • Mucosal Associated Lymphoid Tissue small masses of lymphoid tissue found in intestinal, genitourinary tract and respiratory tract. BALT (BRONCHUS ASSOCIATED LYMPHOID TISSUE ) - includes the tonsils, adenoids GALT (GUT ASSOCIATED LYMPHOID TISSUE ) - Peyer’s patches, appendix CALT (CUTANEOUS ASSOCIATED LYMPHOID TISSUE ) - includes intraepidermal lymphocytes.

THE LYMPHOID SYSTEM. CD – CLUSTER OF DIFFERENTIATION membrane proteins that serve as surface marker for certain blood cells CD MARKERS FOR T-CELL: CD2, CD3, CD4, CD8 CD MARKERS FOR B-CELLS; CD19, CD21, CD23 CD MARKERS FOR NK (NATURAL KILLER) CELLS: CD16, CD56, CD94.

THE LYMPHOID SYSTEM. 2—1. Surface Markers T nd B Cens CDIO CDIG CD19 con CD2S CD4SR CD CD 94 20-28 58 45 85 173-220 T NK cells T cc'B Helper T cells. Mature T cens thymtrytes. su&ct of B cens Thymm•vte sutxes. wtotoxje T eelS B and T cell precurvs marrow strtrnal cells NK cells. B cens dendritic cclB B foaicular ±ndritk ccl& of immatur thymcrytes B ccns follicular dendritic cells Activated T. B cc•IÄ montx*es Most leukocytes Different form on all NK cells subsets of T cells NK cells wb*ts of T cells Involved in T-cca activatitm ks,æia ted with antigen receptor; role in TCR O"al tra nsduction Coreceptor fc' MHC class II: receptor for HIV or modulation of T and B cell signaling Coreceptor for MHC I æotca%t; marker fcy pre—B Low affinity Fc mediates and ADCC hrt of B cell conceptor. trarwiuction mdecuie that B-cell and activation æccptor fcy compkmcnt component C3d; part of B—cell coreceptor with CD 19 of lgE synthesis; of II-I. II-C. and GM—CSF from momn•vtes æccptcy for L-2 khcsion moiecule metiating to peripheral lymphoid organs in T and B cell *tiva Not known Sutwnit of NKG2—A complex invotved in inhi&tion of NK eell cytotoxicity = CD3-< receptc:r cr:mÄ rai:r Rae.

THE LYMPHOID SYSTEM. STAGES OF B-CELL DIFFERENTIATION 1 . Pro-B Cells - markers include CD19, CD45R, TdT , RAG-1and RAG-2 enzymes Tdt - terminal deoxyribonucleotide transferase RAG - recombinase activating gene 2. Pre-B cells - contains pre-B cell receptor that is made up of 2 mu heavy chains and a surrogate light chain whose function is to transmit signals to prevent rearrangement of any other heavy chain genes ..

THE LYMPHOID SYSTEM. ANTIBODY made of monomer as basic unit MONOMER y-shaped molecule made of 2 heavy chains and 2 light chains HEAVY CHAINS GAMMA , ALPHA, MU, DELTA, EPSILON LIGHT CHAIN KAPPA , LAMBDA.

THE LYMPHOID SYSTEM. 3. Immature B-cells - recognized by the appearance of complete IgM molecules on their surface. Specificity of the surface immunoglobulin to be synthesized can already be predicted or noted. Surface markers that can be seen include receptors for complement components such as C3d, CD21. - B-cells capable of producing antibody to self-antigens are deleted in the marrow through APOPTOSIS.

THE LYMPHOID SYSTEM. 4. Mature B cells exhibit IgD and more IgM on their surface as well as MHC Class II products 5. Activated B cells exhibit CD25 on surface. CD25 in turn acts as receptor for IL-2 CD25 + IL-2 --→ proliferation of activated lymphocytes 6. Plasma Cells - large spherical, ellipsoidal cells that contain abundant cytoplasmic immunoglobulins and little to no surface immunoglobulins..

7. Memory B Cells - progeny of antigen stimulated B-cells that are capable of responding to antigen with increased speed and intensity. -SURFACE IgG -long-lived cells IgM - marker of acute/present/active infection IgG - marker of chronic/past infection marker of lifelong immunity DENGUE IgM: + DENGUE IgG: + convalescent stage/recovery phase of infection CD 19- present in all population of B cells..

THE LYMPHOID SYSTEM.

THE LYMPHOID SYSTEM. STAGES OF T CELL DIFFERENTIATION 1. Pro- thymocyte - possess CD44 and TdT 2. Double Negative Thymocyte - lack CD4 and CD8 antigens. - possess CD2, CD5, CD7, CD45R 3. Double Positive Thymocyte - express both CD4 and CD8 antigens on their surface as well as CD3-αβ (TCR) - would undergo Positive and Negative Selection.

THE LYMPHOID SYSTEM. 4. Mature T cells - represents those population of thymocytes that had survived positive and negative selection. - express only 1 of either CD4 or CD8 on their surface. 5 . Activated T cells - express receptors for IL-2 and produce cytokines. Cytokines functions include assisting B cells in the commencement of antibody production, killing of tumors and target cells, rejection of grafts, stimulation of hematopoiesis in the bone marrow and initiation of delayed hypersensitivity allergic reactions. 6. T memory cells.

THE LYMPHOID SYSTEM. NATURAL KILLER CELLS - Larger than T and B cells; contains a kidney shaped nucleus with condensed chromatin and prominent nucleoli. - Has high cytoplasmic:nuclear ratio - Cytoplasm has many azurophilic granules. - Constitutes 5-15% of the circulating lymphoid pool; found mainly in spleen and blood. - No specific surface markers - Possess CD16, CD56, CD 94 - Lack CD3, 4 and 8 - Play a complementary role to CD8+ T cells - Become LAK cells in response to IL-2.

THE LYMPHOID SYSTEM. MECHANISMS OF NK CELL CYTOTOXICITY 1. It is brought about by the balance between activating and inhibitory signals that enables NK cells to distinguish healthy cells from infected or cancerous cells. - Killer cell inhibitory receptors (KIRs) - NKG2D - binds to MICA and MICB proteins on diseased or cancerous cells - If an inhibitory signal is not produced, NK cells will release PERFORINS AND GRANZYMES 2. Antibody Mediated Cell Cytotoxicity - Through binding of IgG-coated cell with CD 16.

THE LYMPHOID SYSTEM. LABORATORY IDENTIFICATION OF LYMPHOCYTES 1. Density Gradient Centrifugation with Ficoll-Hypaque 2. Flourescence Microscopy a. Direct Immunofluorescence - use monoclonal antibodies with a fluorescent tag (e.g. fluorescein and phytoeryhtrin [490 nm]; rhodamine [545 nm]. b. Indirect immunofluorescence - uses unlabeled antibodythat first combines with the antigen by itself and a second antibody that is complexed with a dye..

THE LYMPHOID SYSTEM. 3. Cell Flow Cytometry/Fluorescence Activated Cell Sorter - an automated system for identifying cells based on the scattering of light as cells flow in single file through a laser beam. Fluorescent antibodies are used to screen of subpopulation of T and B cells. Components: a. Sample delivery system b. A laser for cell illumination c. Photodetectors for signal detection d. Computer based management system 4. Rosetting 5. ELISA.

THE LYMPHOID SYSTEM.

REFERENCES:. i . Turgeon, Mary Louise. (2014). Immunology & serology in laboratory medicine, (5th ed.). Missouri : Elsevier . ii. Male, David. (2013). Immunology, (8th ed.). St. Louis, Missouri : Elsevier. iii . Stevens, Christine Dorresteyn . (2010). Clinical immunology & serology : a laboratory perspective, 3rd ed. Philadelphia ; F.A. Davis.

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