Presentation on theme: "Immunology Chapter 3, Lecture 4"— Presentation transcript:
1 Immunology Chapter 3, Lecture 4 Richard L. Myers, Ph.D.Department of BiologySouthwest Missouri StateTemple Hall 227Telephone:
2 Organs of the Immune System Divided on the basis of functionprimary lymphoid organssecondary lymphoid organsPrimary (central) lymphoid organsresponsible for maturation of lymphocytesbone marrowthymusSecondary lymphoid organstrap antigens and allow lymphocytes to respondother lymphoid tissue
4 Primary lymphoid organs Thymuscells entering the thymus are thymocytesthe thymus is a flat, bilobed organ with lobes divided in lobules separated by trabeculaeeach lobule divided into inner (medulla) and outer (cortex) compartmentsthymic hormones cause differentiation and maturation of T lymphocytesa1-thymosin, b4 -thymosin, thymopoietin and thymulin
5 Primary lymphoid organs (cont) Antigenic diversity of TCR results from random gene rearrangements in thymusMost thymocyte progeny undergo programmed cell death by two-step selection process (99%)Neonatal thymectomy results in decrease of circulating T cells and cell mediated immunityDiGeorge’s syndrome in humansnude mice have no thymusThymus reaches its maximal size at pubertythen atrophiesfat content increasesnext slide shows a cross-section of the thymus
7 Bone marrow Bone marrow site of B cell maturationmaturation occurs in the “microenvironment”stromal cells secrete involved cytokinesa selection process eliminates some B cellsThe equivalent in birds is the bursa of FabriciusThe next slide shows the bone marrow
9 Lymphatic system Fluid component of blood is plasma without clotting factors called serumPlasma leaves the capillaries and moves into the interstitial tissuessome returns, the remainder is called lymphThis moves into the lymphatic vesselsReturns to the blood via the thoracic ductAntigens move with lymph into lymphoid tissues
10 Secondary lymphoid organs Before antigenic stimulation, resting B cells are organized into a primary follicleAfter antigenic stimulation, the primary follicle become a larger secondary folliclecontains many proliferating B cells which comprise a germinal centerLymph nodes and the spleen have these structures
11 Lymph nodesSome lymphatic tissue is composed of diffuse collections of lymphocytes and macrophagesOthers organized into lymphoid folliclesContain lymphocytes, macrophages and dendritic cells in reticular networkLymph nodes are divided into cortex, paracortex and medullaMedullary plasma cells produce antibodies
12 Section of enlarged human lymph node (low power view) showing numerous enlarged lymphoid follicles, each composed of a mantle of dark stained small lymphocytes surrounding a pale stained germinal center.
13 Human lymph node showing two enlarged germinal centers containing IgG producing B cells (white) using fluorescent anti-human IgG.
14 Spleen Functions to filter blood and trap blood-borne antigens Composed of red pulp (macrophages and red blood cells) and white pulpWhite pulp surrounds the arteries and forms the PALSSplenectomy predisposes to the individual to several bacterial diseasesThe next slide shows a section of the spleen