The Lymphatic and Immune System Chapter 21.1 Quiz

Lymphatic and Immune Systems

• Immune system: cells and organs that destroy pathogens
• Lymphatic system: vessels, cells, and organs that bring excess fluid to the bloodstream and filter pathogens from the blood

Anatomy of the Lymphatic and Immune Systems

• Lymph: interstitial fluid in the lymphatic system
• Dietary lipids and fat-soluble vitamins are absorbed and travel in lymphatic vessels to the liver
• Lymph node: major staging area for development of critical immune response
• Open-ended capillaries which feed into larger vessels and eventually into the subclavian vein
• Capillaries are simple squamous endothelial cells
• We have 500-600 lymph nodes along those vessels
• Lymph is not pumped – it moves by breathing, muscle contraction, and body movements
• One way valves keep it moving toward the heart (like veins)
• Areas with no lymph vessels are bone marrow, CNS, teeth, and cornea

Organization of Immune Function

• Barrier defenses: skin and mucous membranes, prevent invasion
• Innate immune response: rapid, but non-specific cells
• Adaptive immune response: slower response of lymphocytes
• All leukocytes come from the red marrow (myeloid or lymphoid)
• Phagocytic: ingest pathogens
• Lymphocytes: coordinate adaptive immunity
• Granular: help mediate immune response against parasites and pathogens like bacteria and viruses

Barrier Defenses and the Innate Immune Response

• Barrier defenses: most basic, continuously working (skin and sweat, mouth, stomach, mucosal surfaces, and normal flora)
• Innate immune response: rapid, nonspecific, not always effective
• Adaptive immune response: slower to develop, highly specific, very effective at attacking a wide variety of pathogens
• Skin: to dead and dry for bacteria to grow
• Sweat: wash away pathogens, lower pH, contain toxic lipids
• Oral salivary glands: rich in lysosome
• Stomach: very acidic to kill pathogens
• Mucosal surfaces: traps microbes and debris so they get removed
• Normal flora: prevent pathogens from growing on mucosal surfaces

Innate Immune Cells

• Macrophage: phagocyte that will roam or take a fixed position, first line of defense, they cooperate with the lymphocytes
• Neutrophils: phagocyte that is attracted via chemotaxis, they are like the reinforcements, they also cooperate with lymphocytes
• Monocyte: differentiates into a macrophage or dendritic cell
• Natural killer cells: induce apoptosis in an infected cell by releasing the fas ligand to bind to the fas molecule on the infected cell or by releasing perforins and granzymes

Adaptive Immune Response: T Cells

• Can specifically recognize and attack a wide variety of pathogens, 100 trillion different receptors
• Primary adaptive response: first infection has worse symptoms because adaptive immune system needs to become effective
• Secondary adaptive response: next infection is most likely eliminated before you notice a symptom, this is immunological memory
• Autoimmune disease: adaptive immune response begins to attack your “self” cells

T Cell-Mediated Immune Responses

• In control of adaptive immune response
• Variable region is specific for binding to a single particular antigen
• Antigens: the region on a pathogen that binds to a receptor
• Carb antigen: bacteria and RBC
• Protein antigen: viruses and worm parasites

T Cells

• T cells only recognize antigens on the surface of an antigen presenting cell
• A cell’s enzymes will cleave an antigen into small pieces and present it on the membrane attached to a major histocompatibility complex (MHC) molecule
• The antigen presentation is recognized by T cells
• The antigen presenting cell either takes in extracellular antigens (class II) or a pathogen (class I) that it breaks down to smaller antigens in the lysosome

B Cells and Antibodies

• Antibody: a secreted form of a B cell receptor, there are 5 classes
• B cells can recognize unprocessed antigens and don’t need MHC and antigen presenting cells
• B cells mature in the bone marrow
• Central Tolerance: cells that bind to “self” cells are eliminated in bone marrow
• Peripheral Tolerance: a mature B cell that does bind to a “self” cell will not elicit the response from a Th2 cell to make antibody, that cell will undergo apoptosis
• Mature B cells differentiate into plasma cells
• Plasma cells secrete antibody until they die, terminal differentiation
• Final B cell left is a memory B cell, they react like a memory T cell

Antibody Structure

• 5 classes of antibodies: IgM, IgG, IgA, IgE, and IgD

Response Time

• Initial response takes a few days and is weak
• Secondary exposure has no delay in response and is much stronger

Immunity

• Active immunity: resistance to a pathogen acquired
• Vaccine: killed or weak pathogen that stimulates the body to produce memory cells without suffering through an initial exposure
• Passive immunity: transfer of antibodies to an individual, fetal development or injection, does not lead to immunological memory