Immune System Flashcards
Immune System (Components)
lymphocytes: key defense cells
lymphoid tissue
lymphoid organs: contain lymphocytes, inc. lymph nodes, spleen, tonsils, thymus, as well as aggregated lymphoid nodules in the small intestine and appendix
Lymphocytes
recognize and attack specific foreign molecules (antigens) including pathogens
confers immunity
infectious organisms penetrate the epithelial borders of the body and enter the underlying connective tissue
recognize and act against specific foreign molecules
infectious agents trigger an inflammatory response and are attacked by both lymphocytes and macrophages
Lymphocytes (Classes)
T cells: CD8+ killer cells and CD4+ helper cells; HIV infection lowers the levels of CD4+ helper cells
B cells: develop into plasma cells which produce anitbodies
natural killer cells: detect a lack of “self” cell surface molecules and attack and lyse cells (e.g., tumor cells)
Lymphoid Tissue
important tissue of immune system
specialized type of connective tissue in which vast quantities of lymphocytes gather to fight invading microorganisms
site where most lymphocytes become activated and most effector and memory lymphocytes are generated
Lymphoid Tissue (Locations)
lymphoid organs (except thymus): lymph nodes, spleen, tonsils, as well as aggregated lymphoid nodules in the small intestine and appendix mucosa-associated lymphoid tissue (MALT): in thge mucous membranes of digestive, urinary, respiratory, and reproductive tracts
Lymphocyte Differentiation
site of origin of lymphocytes is bone marrow
primary lymphoid organs
secondary lymphoid organs
antigen activated immunocompetent lymphocytes flowing through lymph and blood
Lymphocyte Differentiation (In Primary Lymph Organs)
in bone marrow and thymus
lymphocytes destined to become B cells remain in red bone marrow where they develop immunocompetence (but still naive/not activated)
lymphocytes destined to become T cells, migrate to thymus where they develop immunocompetence (but still naive/not activated)
Lymphocyte Differentiation (In Secondary Lymph Organs)
immunocompetent but still naive lymphocytes leave the thymus and bone marrow and enter the secondary lymphoid organs (lymph nodes, spleen, tonsils, and other lymphoid tissue)
secondary lymphoid organs store lymphocytes and is site of antigen encounter where B and T cell lymphocytes become activated and effector and memory lymphocytes are generated
Anitgen Activated Immunocompetent Lymphocytes in Blood, Lymph, and Lymphoid Organs
antigen activated immunocompetent lymphocytes (effector cells and memory cells) circulate in the bloodstream, lymph, and lymphoid organs
effector cell lymphocytes: short lived and respond to pathogen immediately and then die
memory cell lymphocytes: long lived and are basis of acquired immunity; wait within lymphoid tissues until antigen is encountered again (can be decades later) and guard against subsequent infections to thus prevent getting infection more than once
Lymphoid Organs
primary lymphoid organs: bone marrow, thymus
secondary lymphoid organs: lymph nodes, spleen, tonsils, aggregated lymphoid nodules in small intestine and appendix
Thymus
secretes thymic hormones thymopoietin and thymosin
differs from other lymphoid organs in that it functions strictly in T lymphocyte maturation, but not T lymphocyte activation
medulla contains Hassall’s (thymic) copuscles that support the development of regulatory T cells which prevent autoimmune responses
thymus is most active in childhood and then activity diminishes as adults age
in elderly only 2% of functional tissue remains
composed of cortex and medulla
Lymph Node
lymph enters thorugh afferent lymphatic vessels and percolates though lymph sinuses
lymphatic and immune systems intersect
most antigenic challenges occur in lymph nodes
antigens activate B and T lymphocytes
antigens are then destroyed
sinuses within lymph nodes contain macrophages living on a reticular fiber network which consume pathogens and foreign particles in the lymph which flows through the sinuses
cortex contains lymphoid follicles, B cells, T cells
medulla contains medullary cords with T cells, B cells, and plasma cells
Spleen
largest lymphoid organ storage of platelets site of hematopoiesis in the fetus site of B cell maturation into plasma cells which secrete antibodies white pulp red pulp
White Pulp (In Spleen)
thick sleeves of lymphoid tissue
lymphoid tissue in spleen is confined to the white pulp
blood-borne antigens are destroyed as they activate the immune response
provides immune function of the spleen
Tonsils
simplest lymphoid organs
four groups of tonsils: palatine, lingual, pharyngeal (adenoids), and tubal tonsils
arranged in a ring to gather and remove pathogens that enter the pharynx through air or swallowed food
crypts of the tonsils trap bacteria, viruses, and particulate matter
underlying lamina propria consists of MALT (mucosa-associated lymphoid tissue)
MALT (mucosa-associated lymphoid tissue) Aggregated Lymphoid Nodules
MALT is present in walls of digestive, respiratory, urinary, and repoductive tracts to fight invading pathogens
in two parts of the intestine, MALT is so large and permanent and packed with lymphocytes that it forms lymph structures:
aggregated lymphoid nodules (Peyer’s patches) located in the walls of the distal part (ileum) of the small intestine
appendix: tubular offshoot of the cecum which has walls rich in defense lymphoid tissue
Disorders of the Lymphatic and Immune Systems
chylothorax: leakage of lymph into the thorax
lymphangitis: inflammation of a lymph vessel
adenitis: inflammation of lymph node
Hodgkin’s disease and non-Hodgkin’s lymphoma: malignancies of lymph nodes
