Louisiana Cuisine

1. Louisiana Cuisine • We eat anything that: • Jumps • Runs • Burrows • Crawls • Flies • Swims frogs “river rat” (nutria?) crawfish, oysters alligator all kinds of birds fish, shrimp, turtle, crab In other words, we love “Fast Food”!

2. Lymphocytes and the Immune SystemFriday, October 3, 2003 • Reading- Anatomy and Physiology- Lymphocytes and Spleen (pp 8-11)

3. Lymphocytes and the Immune SystemFriday, September 27, 2002 • Reading- Anatomy and Physiology- Lymphocytes and Spleen (pp 8-11)

4. CD8+ CD4+ Lymphocytes: Maturation Pathways of B-, T- and Natural Killer (NK) cells •Smallest and second most common group of leukocytes in the bloodstream. •Recognized by their round/oval nuclei with little cytoplasm.

5. Lymphopoiesis Occurs in two distinct phases: •It all starts when the lymphoid stem cell differentiates to form antigen-committed lymphocytes: •This process occurs in the primary lymphoid organs: --T-lymphocytedifferentiation occurs in the thymus, --B-lymphocytedifferentiation takes place in the fetal liver and adult bone marrow.

6. Lymphopoiesis (cont’d) •Antigen-dependent proliferation and development of T- and B-lymphocytes occurs in the secondary lymphoid organs: --spleen; --lymph nodes; and --mucosa-associated lymphoid tissues(which include tissue in the trachea, tonsils, Peyer's patches and the appendix).

7. B-Lymphocyte Development •First step in differentiation of B-lymphocyte stem cell line is the rearrangement of the immunoglobulin heavy chain genes. •Successful rearrangement permits synthesis of IgM chains in the cytoplasm of the cell: --cytoplasmic m chains key features of pre-B lymphocyte. •Rearrangement of the immunoglobulin light chain genes results in the expression of IgM on the cell surface, and this cell is termed the immature (or virgin) B-cell. •The next cell to evolve is the activated/stimulated (adult) B-cell.

8. B-Lymphocyte Development (cont’d) •These activated B-cells can produce all kinds of secreted immunoglobulins. •For a B cell to reach this stage of development, it must first be stimulated by foreign antigenic presentation by an APC. •Differentiation continues to mature plasma cell with extensive endoplasmic reticulum, numerous ribosomes, and an active Golgi apparatus-- signs of an actively secreting cell! •Theplasmacell will actively synthesize and secrete monoclonal antibody of the specificity of the inducing antigen.  •Some plasma cellsrevertto the quiescent state, but can mount a rapid response following further contact with the inducing antigen: memory cells.

9. Antigen and T-cell driven Mitogen inducible Adult B cells Development of B-Lymphocytes Surface Ig Cytoplasmic Ig Stem cell Pre-B cell Virgin B cell Mature plasma cells

10. T-Lymphocyte Development •During fetal development, T-lymphoid stem cells populate the thymus gland where under the influence of epithelial nurse cellsthey proliferate and divide. •These early lymphoid precursors (early thymocytes) express a unique membrane molecule known as Thy-1. These cells lack other membrane proteins unique to T-cells. •Progeny of these lymphoid stem cells progress from the thymus and join the circulation as small T-lymphocytes and go to the peripheral lymphoid tissues.

11. T-Lymphocyte Development (cont’d) •These small T-lymphocytes now await activation by an antigen-bearing-APC cell. •When activated, the first step is the development of a large blast cell commonly known as thelymphoblast. •This blast undergoes division to a prolymphocyte. •Once cell division stops, this cell becomes an immature lymphocyte and it is released into the bloodstream, which then matures into amature active T-cell.

12. Small T cell in lymphoid tissues Activating stimulus (APC epitope presentation) Lymphoblast Prolymphocyte Immature lymphocyte Immature lymphocyte Mature active T cell (Th, Ts, Tc) Memory cell T-Lymphocyte Development

13. T-Lymphocyte Subsets (cont’d) CD4+ T-lymphocytes (~65% of peripheral blood T-cells are CD4+): T-helper lymphocytes (TH) - help and induce activation of B-lymphocytes and secrete IL-2, interferon-gamma act as growth factors; T-delayed-type hypersensitivity (TDTH) - secrete chemotactic factors for macrophages. CD8+ T-lymphocytes (~35% of peripheral blood T-cells are CD8+): Suppressor T-lymphocytes (TS) - act as a brake on TH lymphocytes; Cytotoxic T-lymphocytes (TC) - release cytolytic substances such as perforin directly onto target cells.

14. Natural Killer (NK) Cells •A group of cells classified neither as B- or T-cells, are considered "null cells". NK cells are the biggest of this group: --lack receptors for antigen recognition; --cannot participate in acquired immunity •More closely related to innate immune response. •What makes NK a cell unique is their spontaneous ability to kill tumor cells and virus-infected cells, which produce large quantities of -interferon (IFN-).

15. Anatomy of Lymphatic Organs Thymus --site of T-lymphocyte differentiation --most active during fetal life when it becomes populated with committed lymphoid stem cells --task of populating secondary lymphoid tissue with mature antigen-committed T-lymphocytes is done in the first months of life, after which thymic activity diminishes.

16. Anatomy of Lymphatic Organs (continued) Bone Marrow --in birds, the primary lymphoid organ responsible for the maturation and differentiation of B-lymphocytes is the Bursa of Fabricius. --in humans, induction of B-lymphocyte differentiation is one of the many functions of bone marrow.

17. Anatomy of Lymphatic Organs (continued) Bone Marrow •In 1957, Glick and colleagues were trying to define the function of the Bursa of Fabricius in chickens: --it was known to be active early in life and the largest in size. They removed the organ and nothing discernable happened. --these adult birds were recruited to a student exercise to raise antibodies, and they failed to synthesize an antibody response to the antigen. --this strange but very important observation may be one of the most important one made in defining the role of B-lymphocytes as a mediator of humoral immunity, and it was discovered because of a lack of school resources (for teaching purposes) to buy new chickens!

18. Anatomy of Lymphatic Organs (continued) Spleen •Largest of the lymphoid organs, performs a number of functions, including: (1) blood filtration- selectively removes senescent or antibody-coated red cells from the circulation. (2) blood pooling- 1/3 of the total platelet mass is here, and it is in dynamic equilibrium with the circulating pool. About 5% of total red blood cell mass is here.

19. periarteriolar lymphatic T-cell sheath (PALS) Anatomy of Lymphatic Organs (continued) Spleen Function (continued) (3) immune function- filtering action collects and concentrates blood-born foreign antigens for processing by the immune system. Major site of antibody synthesis within the body. (4) hematopoietic function- normally is a hematopoietic organ in utero, can resume under extreme conditions.

20. Anatomy of Lymphatic Organs (continued) •red pulp consists mainly of cords and sinuses, which are simply vascular spaces lined with macrophages. All blood cells must move between these sinuses and macrophages. •the central arteries are surrounded by white pulp, which is made up of mainly lymphoid tissue with loosely packed lymphocytes, containing both B- and T-lymphocytes. •boundary between white and red pulp is the marginal zone and is rich in dendritic APC's that capture, process and present foreign antigen for T-cell stimulation.

21. Anatomy of Lymphatic Organs (continued) Lymph Nodes •Lymphatic circulatory systems act as a drainage system for excess interstitial fluid or lymph. •Many structural similarities to the blood circulatory system: --smallest lymphatic vessels are called lymphatic capillaries and they penetrate deep into almost all tissues; --lymphatic capillaries drain into larger vessels equivalent of veins; --largest vessels, like arteries, are muscular and actively pump lymph into the thoracic duct.

22. Anatomy of Lymphatic Organs (continued) •Lymph nodes are small bean-shaped structures that are found in clusters at junctions in the lymphatic circulatory systems.