Lymphatic system

• The lymphatic system consists of two semi-independent parts: lymphatic vessels and lymph nodes.
• Swelling (edema) is caused by damaged cells releasing inflammatory chemicals such as histamine and kinin, which cause blood vessels to dilate, capillaries to become leaky, and phagocytes and white blood cells to move into the area in a process called positive chemotaxis.
• The functions of the inflammatory response include preventing the spread of damaging agents, disposing of cell debris and pathogens through phagocytosis, and setting the stage for repair.
• The process of the inflammatory response involves neutrophils migrating to the area of inflammation by rolling along the vessel wall, following the scent of chemicals from inflammation.
• Neutrophils squeeze through the capillary walls by diapedesis to sites of inflammation.
• Lymphoid tissues and organs are part of the lymphatic system which transports escaped fluids from the cardiovascular system back to the blood and plays essential roles in body defense and resistance to disease.
• Lymph consists of excess tissue fluid and plasma proteins carried by lymphatic vessels.
• If fluids are not picked up, edema occurs as fluid accumulates in tissues.
• Lymphatic vessels (lymphatics) pick up excess fluid (lymph) and return it to the blood.
• Lymphatic vessels form a one-way system, lymph flows only towards the heart.
• Lymphatic capillaries weave between tissue cells and blood capillaries, and their walls overlap to form flap-like mini valves.
• Lymphatic collecting vessels collect lymph from lymph capillaries.
• Lymph nodes filter lymph before it is returned to the blood.
• Lymph nodes are part of the body's defense system, macrophages engulf and destroy bacteria, viruses, and other foreign substances in lymph, while lymphocytes respond to foreign substances in lymph.
• Most lymph nodes are kidney-shaped, less than 1 inch long, and are buried in connective tissue, surrounded by a capsule, and divided into compartments by a trabeculae.
• Cortex contains follicles, a collection of lymphocytes, and germinal centers that enlarge when antibodies are released by plasma cells.
• Major types of transplants, or grafts, include autografts, isografts, allografts, xenografts, and transplants are done based on blood group and tissue matching to ensure the best match possible.
• A 75% match is needed to attempt a graft.
• Organ transplant is followed by immunosuppressive therapy to prevent rejection.
• Autoimmune diseases occur when the body’s self-tolerance breaks down, the body produces auto-antibodies and sensitized T lymphocytes that attack its own tissues, and most forms of autoimmune disease result from the appearance of formerly hidden self-antigens or changes in the structure of self-antigens, and antibodies formed against foreign antigens that resemble self-antigens.
• Lymphatic vessels form by budding off from veins.
• Lymph nodes are present by the fifth week of development.
• The thymus and the spleen are the first lymphoid organs to appear in the embryo.
• Other lymphoid organs are poorly developed before birth.
• The immune response develops around the time of birth.
• The ability of immunocompetent cells to recognize foreign antigens is genetically determined.
• Stress appears to interfere with normal immune response.
• Efficiency of immune response wanes in old age, and infections, cancer, immunodeficiencies, and autoimmune diseases become more prevalent.
• Passive immunity occurs when antibodies are obtained from someone else, such as naturally acquired from a mother to her fetus or in the breast milk, or artificially acquired from immune serum or gamma globulin (donated antibodies).
• Immunological memory does not occur in passive immunity.
• Passive immunity provides short-lived protection, typically lasting 2-3 weeks.
• Monoclonal antibodies are antibodies prepared for clinical testing for diagnostic services, produced from descendants of a single cell line, and exhibit specificity for only one antigen.
• Examples of uses for monoclonal antibodies include cancer treatment, diagnosis of pregnancy, and treatment after exposure to hepatitis and rabies.
• Antibodies, also known as immunoglobulins or Ig, constitute gamma globulin part of blood proteins, are soluble proteins secreted by activated B cells (plasma cells), and are formed in response to a huge number of antigens.
• The structure of an antibody consists of four polypeptide chains, two heavy and two light, linked by disulfide bonds to form a T- or Y-shaped molecule.
• Each polypeptide chain in an antibody has a variable (V) region and a constant (C) region.
• Variable regions in an antibody form antigen-binding sites, one on each arm of the T or Y.
• Constant regions in an antibody determine the type of antibody formed (antibody class).
• Antibodies of each class have slightly different roles and differ structurally and functionally.
• There are five major immunoglobulin classes (MADGE): IgM, IgA, IgD, IgG, and IgE.