circular system

• blood system
• travels two ways
• takes oxygen and nutrients out, brings CO2 and waste back
• delivers water to all parts of the body
• immune cells use this system

lymphatic system

• only a return system (one way)
• flows from the tissues back to the central body
• brings water and other nutrients carried within the water back to the central body
• immune cells use this system too

cells involved in acquired immunity

lymphocytes

• T-cells
• B-cells

cells involved in innate immunity

phagocytes

• macrophages
• dendritic cells
• neutrophils

ways cells recognize foreign bodies

• PRR (pattern recognition receptors)
• Peptidoglycan
• LPS (lipopolysaccharide)
• PAMP (pathogen-associated molecular patterns)

phagolysozome

• phagocytosis occurs: membrane engulfs the bacterial cell
• lysozyme hurts the bacterial cell 

acquired immunity

• specificity: recognized antigens
• memory: faster and more  dramatic healing the second exposure
• tolerance: can differentiate between self and foreign antigens

receptors used to bind to antigens

• all can recognize specific foreign molecules (antigens)
• MHC1: found on every nucleated cell 
• MHC2: phagocytes and B cells
• T-cell receptors: found on T cells
• B-cell receptors: found on B cells, specialized antibodies
• antibodies: not found on cells, but are released by the cells and distributed throughout the body

antigen-presenting cells

• cells that have a protein that will be cut up, and a small piece will be taken out
• this piece of protein is put on the surface and associated with an MHC1
• a foreign antigen will be recognized by a T-cell
• Tcytotoxic cell releases granules that lead to apoptosis

T-Helper 1 Cells

• phagocytic cells that puts foreign bacteria into phagolysozome, where it gets cut into little pieces
• has a T-cell receptor that recognized foreign antigens
• cytokines are released, which activate the phagocyte and recruitment of other phagocytes

T-Helper 2 Cells

• these look for B cells that have MHC2 with an antigen
• the B cell receptor binds to the foreign antigens, cuts it up, takes it out
• TH2 cells produce cytokines that activate the B cell
• B cell divides-producing plasma cells which make up antibodies
• these antibodies get released into the body, bind to bacterial/virus infected cells, or toxin proteins
• differentiates into memory cells, that put out the same B cell receptor