Lymphatics lectures(1)

Lymphatics lectures(1) - 4/4/11 The lymphatic system The...

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Unformatted text preview: 4/4/11 The lymphatic system The lymphatic system The lymphatic system is a complex of organs, tissues and cells that are involved in the IMMUNE RESPONSE TWO LECTURES: The principal cells in immune responses are - LYMPHOCYTES 1.  Basics of the immune response - MACROPHAGES 2. Histology of the lymphatic tissues and organs These cells are involved in two basic immune mechanisms: 1.  Humoral response 2. Cell mediated response 1 4/4/11 Cell mediated response is mediated by T lymphocytes Humoral response is mediated by B lymphocytes and involves the synthesis and secretion of antibodies There are a number of populations of T cells Helper T cells are activated by antigens and in turn …….. Antibodies act is a number of ways: - precipitate soluble antigens by crosslinking - agglutinate particulate antigens (and cells) - opsonise bacteria (bind to bacterial surface) - neutralise viruses (prevent viruses from adhering to cell membrane ANTIBODY STRUCTURE 1. Activate B cells 2. Generate 2 major effector mechanisms - cytotoxic cells - kill foreign cells - cells that release lymphokines - regulate many aspects of immune response e.g. attract and activate macrophages, stimulate proliferation and differentiation of B cells etc Antibodies (Ab) form complexes with antigens (Ag) Each Ab has two Ag combining sites antigen -  Antibodies are made up of 2 identical heavy chains and 2 identical light chains antibody - Each chain has a variable and a constant region 2 4/4/11 Each Ab has two Ag combining sites Antibodies belong to the immunoglobulin (Ig) class of proteins Ab/Ag held together - hydrophobic bonds - Van der Waals forces - electrostatic bonds - hydrogen bonds Each Ag has a number of epitopes variable region ab constant region ab Antibodies are made up of 2 identical heavy chains and 2 identical light chains and have variable and constant regions ag ab Optimum proportions (2Ab : 1 Ag) ab ag ag ab ab ag ab ab ab aggregate formation ag - the variable region - combines with antigen - the constant region determines class of immunoglobulin (IgG, IgA, IgM, IgD, or IgE Instructive Theory Ag combining site DNA Antigen release Ag excess • Small aggregates • Minimal precipitation Optimal proportion • Large aggregates • Heavy precipitation Common gene Standard unfolded γ-globulin Folds to shape of antigen template and stabilized (eg. by S-S bonds) Specific Antibody Ab excess • Small aggregates • Minimal precipitation 3 4/4/11 Instructive Theory Ag combining site DNA Clonal selection model Antigen release Common gene Folds to shape of antigen template and stabilized (eg. by S-S bonds) Standard unfolded γ-globulin Specific Antibody Proposed by Macfarlane Burnet to explain the selective theory of antibody formation Selective Theory Ag combining site DNA 1. Each lymphocyte has genetic information to make one antibody 2. Antibodies act as cell surface receptors Spontaneous folding 3. There are many different lymphocytes in absence of antigen 4. Antigen binds to antibody that is a good fit Specific gene ‘derepressed’ by antigen ANTIGEN 1 B CELLS 5. Antigen binding stimulates proliferation and differentiation Specific Antibody Ig peptide chains with specific amino acid sequence 2 Antibody on B cell surface acts as receptor for antigen 3 4 Lymphoid stem cells arise first in - YOLK SAC, then migrate to - The antigen will form stable complex with antibody that is good fit - LIVER - SPLEEN Antigen binding causes clonal explansion of B lymphocyte 1 B lymphocyte 1 specialises into a highly secretory Plasma cell Origin and differentiation of T and B cells - BONE MARROW 1 1 1 1 1 1 1 Antibody titre (concentration) substantially increases and antigen is inactivated 1 4 4/4/11 Interaction of T or B Cells with Ag Small lymphocyte MORPHOLOGICAL CHANGES T cells B cells - Detector cells Small lymphocytes Ag interaction Lymphoblast Large lymphocytes proliferation Prolymphocyte polymorph FUNCTIONAL CHANGES Plasmablast Medium lymphocytes Proplasmacyte Differentiation Small lymphocyte (recirculating) Plasma cell - Effector cells - Memory cells (assume a small lymphocyte morphology and hang around Small lymphocyte and red blood cells Plasma cell - characteristically has large amount of cytoplasm and a light staining region next to the round nucleus 5 4/4/11 MACROPHAGES There are a variety of forms of macrophages Two main activities 1.  Phagocytic (microbe munchers) e.g Kupffer cells of the liver have plenty of lysosomal granules and are actively phagocytic 2. Presentation of antigens e.g dendritic macrophages in lymph nodes have elongated cellular processes and a large surface area for presentation of antigen and activation of lymphocytes Antigen uptake….antigen processing…antigen presentation Plasma cell - produces antibodies - has prominent Golgi and rough endoplasmic reticulum (RER) - has a distinctive round nucleus with clockface distribution of chromatin Macrophage with large amount of cytoplasm containing lysosomes and phagocytosed material 6 4/4/11 Lymphoid organs and tissues Central lymphoid organs produce detector cells - thymus produces T cells - Bursa of Fabricius (only in chickens) produces B cells THYMUS Peripheral lymphoid organs and tissues - most active in newborn: Screen for antigens - blood……spleen - lymph…..lymph nodes - tissue fluids..other lymphatic tissues - held together by reticular epithelial cells with long processes and desmosomes - abundant cell division and cell death 7 4/4/11 Active thymus is lobulated with each lobule having a cortex and medulla Thymus Gland septa medulla Reticular epithelial cells form the supporting framework of the thymus cortex Hassall’s corpuscles are distinguishing features of the thymus 8 4/4/11 Hassall’s corpuscles are aggregates of reticular epithelial cells Thymus from mature individual T cell production is substantially reduced and connective tissue and fat cells are abundant Thymus undergoes involution (ageing) Thymus from mature individual Neonate - very active Loss of distinction between cortex and medulla puberty Progressive increase in fat cells and connective tissue at expense of generation of T lymphocytes Post-puberty Fat cells Connective tissue Thymus shows limited activity in adult - unless major stress experienced 9 4/4/11 Peripheral lymphoid organs and tissues SPLEEN…….filters blood Screen for antigens - blood……spleen - lymph…..lymph nodes - tissue fluids..other lymphatic tissues Spleen has red pulp and white pulp Spleen White pulp 10 4/4/11 Fibromuscular capsule Germinal centres White pulp capsule White pulp trabeculum Red pulp Central artery 11 4/4/11 Penicillus in red pulp sinusoid Open circulation Sinusoids Central (white pulp) artery White pulp sinusoid penicillus Capilliary region Arteriolar region Ellipsoid Closed circulation Ellipsoid region of penicillus sinusoid 12 4/4/11 pid=S0717-9 Splenic arteries Trabecular arteries Sinusoidal endothelial cells (loosely packed so that blood cells can enter and exit) White pulp (central) arteries Penicilli -arteriolar -ellipsoid -capilliary (connect to sinusoids - open circulation and closed circulation models) sinusoids Trabecular veins Splenic veins Peripheral lymphoid organs and tissues Lymph nodes…..filter lymph Screen for antigens - blood……spleen - lymph…..lymph nodes - tissue fluids..other lymphatic tissues 13 4/4/11 Lymph nodes are located along lymphatics - each lymph node is about the size of an almond Characteristically nodules are common in the lymph node cortex - many with germinal centres Lymph Node Subcapsular Lymph node capsule Subcapsular sinus trabeculum Lymph nodule 14 4/4/11 Lymph node paracortex 1. Large lymphocytes, 2 dividing large lymphocytes, 3-4 medium lymphocytes, 5 small lymphocytes capsule Subcapsular sinus trabeculum Lymph nodule Reticular fibres Lymph node medulla - cluster of B cells Scanning electron micrograph of lymphatic sinus 1, plasma cell, 2 proplasmacyte, 3 small lymphocyte trabecular fibres lymphocytes 15 4/4/11 Peripheral lymphoid organs and tissues Nodular - no capsule present - found - tonsils - Peyer’s patches - appendix singly and in clusters such as - Screen for antigens - blood……spleen Other lymphatic tissues - lymph…..lymph nodes - tissue fluids..other lymphatic tissues Diffuse - found in connective tissue of almost all organs - Densely infiltrated - lightly infiltrated Tonsils - palatine, pharyngeal (adenoids), lingual Tonsils - tonsils are comprised of a cluster of lymphatic nodules underneath oral mucosa - no capsule pharyngeal epithelium 16 4/4/11 Peyer’s patches - lymphatic nodules in submucosa of small intestine villi Lymph Nodules Lymph nodules Elephantiasis - caused by blockage of lymphatic vessels by parasitic nematode worms 17 4/4/11 18 ...
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This note was uploaded on 05/23/2011 for the course PSYC 2011 taught by Professor > during the Three '11 term at University of Sydney.

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