BIOL 1209 Chapter : 20140408 160109
Chapter 43- The immune system
Concept 43.1- In innate immunity, recognition and response rely on traits common to groups
of pathogens
• (Adaptive immunity only with vertebrae)
• Barrier defenses
o Skin is a barrier to microbes
o Continuously shed, removing microbes that gain a foothold on the skin
o Many skin secretions contain natural antibiotics
▪ Give the skin a pH between 3-5
▪ Also has lysozyme
o Mucus membrane secretions contain lysozymes
o Mucus traps microbes entering the nose or mouth
o Respiratory tract cilia sweep mucus and microbes away from lungs
• Internal defenses- phagocytes
o Phagocytes- types of leukocytes
o Phagocytosis- ingestion of invading microorganisms by certain types of white
bloods
o 4 types of phagocytic WBCs
▪ Neutrophils
▪ Macrophages
▪ Eosinophils
▪ Dendritic cells
• Internal Defenses: recognizing pathogens
o Toll-like receptors
▪ Bacteria- lipopolysccharides, flagellin
▪ Viruses- CpG DNA, dsRNA
• Internal defenses- Antimicrobial proteins
o These proteins function by attacking microbes directly or by impeding
reproduction
▪ Complement system- causes lysis of invading cells and helps trigger
inflammation
▪ Interferons- released by virally-infected cells
• Helps healthy cells resist infections
• Activates macrophages
• Internal defenses- inflammatory response
o Chemical signals released by macrophages (cytokines) and mast cells
(histamines) cause capillaries to become more permeable
o Fluid, antimicrobial proteins, and clotting elements enter site
o Cytokines attract more phagocytic cells
o Phagocytic cells engulf microbes and damaged cells
• Internal defenses- natural killer (NK) cells
o Attracts body cells that are virally infected or cancerous
o Releases chemicals that initiates apoptosis (i.e. cell death)
Conecept 43.2- in adaptive immunity, lymphocyte receptors provide pathogen-specific
recognition (found only in vertebrates)
• Antigens and epitopes
o Antigen- any foreign molecule that is specifically recognized by lymphocytes and
elicits a response from them
o Epitope- accessible region of an antigen to which an antigen receptor or
antibody binds (surface of pathogen has antigen on it, with a region of epitope)
