Minia University Faculty of Agriculture

1. Minia UniversityFaculty of Agriculture CHICKEN’S LYMPHATIC SYSTEM AND IMMUNITY By Akrum Hamdy, Guillermo Tellez and B. M. Hargis akrum312@hotmail.com www.Kenanaonline.Com/WS/AkrumHamdy

2. Up to 80-90th of XX century, lymphatic system was considered as a part of vascular system.In the second half of XX century, detailed research of the organs of lymphatic system, and of lymph nodes in particular, lead to the understanding of a defensive role of this system .

3. Lymphatic System Consists of • Lymph • Lymphatic vessels • Lymphatic tissue • Lymphatic nodules • Lymph nodes • Spleen • Thymus • Bursa of Fabricius

4. Importance of the Lymphatic System Two most important functions 1- Maintenance of fluid balance in the internal environment. 2- Immunity

5. The Lymph System All body tissues live in a liquid environment, both in the cells and surrounding them. During cellular metabolism, waste products, including carbon dioxide and other substances are routed back through the blood stream to be eliminated. In addition to the elimination provided for by the circulatory system, a second pathway for the removal of tissue fluids from the body is achieved though the lymph system.

6. The function of the lymph system The function of the lymph system is to remove excess tissue fluids that do not return through the circulatory system. In addition, the lymph system is responsible for absorbing protein form this fluid and returning it to the blood. Like the circulatory system, the lymphatic system is made up of a series of capillaries and lymphatic vessels. Unlike the circulatory system, the lymph system does not have a heart to propel lymph (tissue fluids that have entered the lymphatic system) through the system.

7. Functions of the lymphatic system • Excess interstitial fluid enters lymphatic capillaries becomes lymph. • Absorption of fat and other substances from digestive tract • Lymphatic vessels carry lymph away from tissues

8. Fluid Movement

9. The movement of lymph is based upon either the volume of fluid within the lymph vessel or by mechanical means, i.e. through movement of the skeletal muscles, where the muscles compress the lymphatic vessels and drive the lymph forward. • Throughout the lymph system, can be found a series of lymph nodes, whose function it is to filter the lymph, trapping and destroying bacteria and other foreign particles.

10. Lymph nodes can be found throughout the body, but tend to be grouped together. • Major groupings of lymph nodes can be found in the neck (cervical nodes), in the armpits (axillary nodes), near the trachea and bronchial tubes (tracheobronchial nodes), in and around the intestines (mesenteric nodes) and in the groin area (Inguinal nodes).

11. Importance of the lymphatic system in maintaining fluid balance. • Plasma filters into the interstitial spaces from blood flowing through the capillaries. • Much of this interstitial fluid is absorbed by tissue cells or reabsorbed by the blood before it flows out of the tissue. • A small amount of interstitial fluid is left behind. • If this would continue over even a brief period of time, the increased interstitial fluid would cause massive edema. • This edema would causes tissue destruction or death • This problem is avoided by the presence of lymphatic vessels that act as "drains" to collect the excess fluid and return it to the venous blood just before it reaches the heart.

12. Lymph organs • Lymph organs include the bone marrow, lymph nodes, spleen, and thymus. Bone marrow contains tissue that produces lymphocytes. B-lymphocytes (B-cells) mature in the bone marrow. T-lymphocytes (T-cells) mature in the thymus gland. Other blood cells such as monocytes and leukocytes are produced in the bone marrow. • Lymph nodes are areas of concentrated lymphocytes and macrophages along the lymphatic veins. The spleen is similar to the lymph node except that it is larger and filled with blood.

13. Thymus The thymus gland is the site in which T-lymphocytes develop and mature before birth and is most active prior to puberty. The thymus secretes the hormone thymosin, which promotes the growth of lymphocytes and lymphoid tissue throughout the body.

14. Spleen The spleen is an organ that contains lymphoid tissue and is designed to filter blood. It is located in the upper left quadrant of the abdominal cavity and is protected by the ribs. One function of the spleen is to filter out old red blood cells. The spleen also harbors phagocytes, which engulf bacteria and other foreign particles. The spleen also serves as a reservoir of blood in cases of emergency.

15. Vermiform Appendix • Although the function of the vermiform appendix is unknown, the appendix is rich in lymph tissues. The appendix is located at the end of the cecum, which is part of the large intestine

16. General Defenses • Barriers to entry are the skin and mucous membranes. The skin is a passive barrier to infectious agents such as bacteria and viruses. The organisms living on the skin surface are unable to penetrate the layers of dead skin at the surface. Tears and saliva secrete enzymes that breakdown bacterial cell walls. Skin glands secrete chemicals that retard the growth of bacteria. Mucus membranes lining the respiratory, digestive, urinary, and reproductive tracts secrete mucus that forms another barrier. Physical barriers are the first line of defense.

17. The Immune System • The immune system is part of general body defenses against disease. It functions by recognizing viruses and bacteria and converting that information into hormones that activate the immune process. • This response can be both specific, where the body responds only to certain agents and no others as well as nonspecific, where the body works to defend itself any harmful agent that enters the body.

18. Immunity • Immunity is the ability of an individual to resist or overcome the effects of a particular disease or other harmful agent. • Immunity, however, is a selective process, with one being immune to one disease and not necessarily another. • Immunity can be either inborn, which is due to inherited factors, or acquired. Acquired immunity develops during chick’s lifetime as they encounter various harmful agents and successfully fight them off.

19. Lymphocytes • White blood cells known as lymphocytes arise from by mitosis of stem cells in the bone marrow. Some lymphocytes migrate to the thymus and become T cells that circulate in the blood and are associated with the lymph nodes and spleen. • B cells remain in the bone marrow and develop before moving into the circulatory and lymph systems. B cells produce antibodies.

20. Cell-mediated immunity is mainly a function of A. B cells B. T cells C. Macrophages D. Neutrophils

21. B Cells • B cells were so named because they were first studied in the bursa of Fabricius, an organ unique to birds. In humans, B cells actually originate in the bone marrow. • The B cells have two major jobs: they maintain a memory database, and they create complex protein structures that are used as weapons against threats and invaders. These complex structures are called antibodies, about which more is coming.

22. B cells keep a record of every single interaction chicken immune system has ever had. This means that within chicken body, a record of every germ and virus chick has ever encountered, every protein ever eaten, every piece of pollen ever inhaled, has been stored in a memory bank-not in chicken’s brain, but in chicken immune system. Think about it: for each of these interactions, there is a B cell floating around inside their body that has retained a memory of the encounter

23. What is in the lymphatic system? • Lacteals and lymphatic capillaries • Overlapping epithelial cells • Lymph vessels and ducts • What happens if blockage occurs? • See next slide!

24. What is in the lymphatic system? • Lymph nodes • Filters lymph fluid for antigens, bacteria, etc. • B-lymphocytes made here • Some T-lymphocytes and macrophages congregate • Afferent (more) and efferent (less) vessels • lymph fluid exits through hilum • Common site for cancer—Why? • Hodgkin’s lymphoma: lymph node malignancy • Etiology unknown • Non-Hodgkin’s lymphoma: all other cancers of lymphoid tissue • Multiplication/metastasis of lymphocytes • 5th most common cancer

25. What is in the lymphatic system? • Spleen: dense sieve of reticular CT • Functions • Erythropoiesis in fetus • Stores platelets • Salvages and stores RBCs parts for recycling (RBC graveyard) • Red pulp • Dispose of damaged/dead RBCs and pathogens • Old RBCs aren’t flexible enough to get through sieve • White pulp • Lymphocytes and macrophages • B-cells proliferate here • If splenectomy: liver and marrow take over duties

26. What strategies does the immune system use? • Non-specific immunity • Responds without caring about specific type of threat • Specific immunity • Tailored to specific pathogens; based on memory • Two types • Antibody-mediated immunity (humoral response) • Cell-mediated immunity

27. What’s behind non-specific immunity? • External barriers • Skin • Keratin is tough to penetrate • Low pH (lactic acid), very dry, nutrient-poor • Anti-microbial proteins: defensins from neutrophils • Mucus • Urine, saliva, tears and mucus • Contain lysozyme (dissolves peptidoglycan wall) • Viscous areolar CT matrix

28. What’s behind non-specific immunity? • Phagocytes • Macrophages: tissue-living monocytes • Neutrophils: digestion and killing zone (H2O2; superoxide ion and hypochlorite (bleach)) • Eosinophils: less avid digesters • Basophils and mast cells: it mobilize other WBCs (via histamine and heparin) • some phagocytosis • Natural Killer cells (NK cells): type of T-cell • Only attack infected or cancerous host cells

29. What’s behind non-specific immunity? • Inflammation • Redness, swelling, heat, pain • Bradykinin: pain stimuli from mast cells • Histamine: what two things does it do? • Leukocyte migration • Margination • http://www.med.ucalgary.ca/webs/kubeslab/home/ • Diapedesis: http://www.constantinestudios.com/animation4.html • Chemotaxis • Phagocytosis

30. What is specific immunity? • Specific response • Memory for future reinvasion • Antibody-based • B cells primary (but not only) factors • Cell-mediated • T cells only

31. What are antibodies? • Antibody: gamma globulin (protein) which complexes with a specific antigen • AKA Immunoglobin (Ig) • Antigen (Ag): any molecule which causes an immune response • Not necessarily always dangerous antigen • Epitopes: different regions where different antibodies bind • Haptens: too small on their own but can bind with host molecules and cause immune response • Detergent, poison ivy, penicillin

32. What do antibodies look like? • Protein with quaternary structure • Two light chains, two heavy chains • Each chain has variable region • Combine to form antigen-binding site • Remainder of chains = constant region

33. What are the five antibody classes? • IgA: prevents pathogens from sticking to epithelia • Can form dimers • IgD: antigen receptor in B-cells • IgE: stimulates basophils/mast cells • Secrete histamines, also causes allergic response • IgG: most common antibody (75-85%) • Primary Ig of secondary immune response • IgM: antigen receptor in B-cells • Can form pentamers • Predominant Ig of primary immune response • Includes anti-A and Anti-B of ABO blood groups

34. Antibodies are defense substances produced by the _C__ cells. • A. T-lymphocytes • B. Monocytes • C. B-Lymphocytes • D. Leukocytes

35. What are T cells? • Migrate from marrow and develop in thymus • Have antigen receptors on PM = immunocompetent • Mitosis produces clones • Clonal deletion destroys self-reactive clones • Good at destroying cells and stimulating B cells • They do NOT secrete antibodies as B cells do • T cell types movie

36. What are B cells? • From marrow: colonize lymph tissues, organs when mature • Developing B cells synthesize PM antibody • Each cell has a different antibody covering it • Mitosis: immunocompetent clones • One B cell responds to only one antigen • Serve as antigen-presenting cells (APC) • So do macrophages • Lets T cells “see” the antigen • Secrete antibodies into blood, but do NOT kill cells as T cells do • B cell types movie

37. What happens in a cell-mediated response? • The key players: • Antigen-presenting cell • Cytotoxic (killer) T cells (CD8 cells) • Helper T cells (CD4 cells) • The ones attacked in HIV infection • Suppressor T cells • Memory T cells • T cells are “blind” to free-floating antigens

38. What happens in a cell-mediated response? • The key events: • Surveillance and recognition • Attack • Memory

39. What happens during the memory phase? • During cloning, some T cells are put in reserve • Thousands of these “hang out” in the body • Launch immediate attack if same antigen appears again • Attack is so quick, no symptoms develop

40. The Lymphatic System includes • Lymph nodes located along the paths of collecting vessels. • Isolated nodules of lymphatic patches in the intestinal wall. • Specialized lymphatic organs such as the tonsils, thymus, and spleen.

41. The lymphatic system differs from the circulatory system in that the lymphatics do not form a closed ring or circuit. • Instead, begin blindly in the intercellular spaces of the soft tissues of the body.

42. Fluid Leaves Capillary Cells Blood Blood Capillary

43. Capillaries

44. Functions of Lymphatic System • Drain fluid from around cells • Absorb fat from intestines • Circulate lymph • Filter lymph • Immunity

45. Lymph • Fluid of the lymphatic system • Similar to blood plasma and interstitial fluid

46. Lymphatic Vessels • Transport lymph • Lymph is returned to the circulatory system at either the right or left subclavian veins

47. Thymus • Programs some lymphocytes to develop into T-cells

48. Nonspecific Body Defenses • Skin • Acid • Stomach • Vagina • Mucus • Saliva • Tears

49. More Nonspecific Defenses • Phagocytosis • Complement • Fever • Inflammation

50. Complement