PY 105 Chapter Notes - Chapter 11: Thoracic Duct, Complement System, B Cell
Lymphatic System
• One way flow system
• Begins with tiny lymphatic capillaries in all the tissues of the body that merge to form larger
lymphatic vessels
• Merge to form large lymphatic ducts
• Suction pump to retrieve water, proteins and white blood cells
• Fluid in lymphatic vessel is called lymph - filtered by lymph nodes
• Lymph nodes contain millions of white blood cells which initiate an immune response
• Large lymphatic ducts merge to form the thoracic duct, largest lymphatic vessel in the chest
Immune System
• Three types of immunity:
o Innate
• General, non-specific protection the body provides against various invaders
• Skin
▪ Excellent barrier against the entry of microorganisms
▪ Tears, saliva, and blood contain lysozyme, enzyme that kills some bacteria by
destroying their cell walls
▪ Extreme acidity of the stomach destroys many pathogens which are ingested
▪ Macrophages and neutrophils phagocytize microorganisms
▪ Complement system is a group of 20 blood proteins that nonspecifically bind to
the surface of foreign cells, leading to their destruction
o Humoral
• Specific protection by proteins in the plasma called antibodies (Ab) or
immunoglobulins (Ig)
• Antibodies recognize and bind to microorganisms leading to their destruction and
removal from the body
• Light chains and heavy chains joined by disulfide bonds
• Constant region and variable (antigen binding) region
• Each antibody forms a unique variable region that has a different binding specificity
• The molecule that an antibody binds to is known as antigen (Ag)
• The specificity of antigen binding is determined by the fit of antigen in a small three-
dimensional cleft formed by the variable region of the antibody molecule
• The small site that an antibody recognizes within a larger molecule is called an epitope
▪ Binding of antibody may directly inactivate the antigen
▪ Binding of antibody can induce phagocytosis of a particle by macrophages and
neutrophils
▪ The presence of antibodies on the surface of a cell can activate the complement
system to form holes in the cell membrane and lyse the cell
• Antibodies are produced by a type of lymphocyte called B cells
• Immature B cells are derived form precursor stem cells in the bone marrow
• The genes that encode antibody proteins are assembled by recombination from many
small segments during B cells development
• There are many different B cell clones
• When antigen binds to the antibody on the surface of a specific immature B cell, that
cell is stimulated to proliferate and differentiate into two kinds of cells: plasma cells
and memory cells
▪ Plasma cells - actively produce and secrete antibody protein into the plasma
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