Non-specific Immunity

“First Line” of Defense

• Physical barrier on all surfaces of body exposed to external world

• What are they?– Skin– Mucous membranes—nasal, respiratory– Lining of mouth– Lining of gut– Lining of vagina/urethra– Surface of eye

Barrier Membranes

Skin

How do barrier membranes keep bacteria out?

• Chemical barrier—antibacterial secretions• Cellular barrier—cells tightly packed and

sloughed off (10B skin cells/day=250 g./year)• Physical barrier—thick, mucousy and sticky

secretions trap bacteria• Resident microbes—have commensal or

mutualistic bacteria and fungi that are normally present and out-compete potential pathogens

Second Line of Defense

• Phagocytosis

• Inflammation

• Complement

• Fever

• All work tightly with specific immunity (coming next)

• Phagocytes move through blood and lymph and into connective tissues (part of inflammation response as cells and fluid move out of capillaries into surround aleolar tissues--diapedesis)

Phagocytosis

•Langerhans cells in skin•Phagocytes in blood•Microglial cells in CNS

Complement

• Group of free proteins in blood that respond to antigen/antibody complex (huh?—coming soon)

• Cascade of reactions eventually makes MAC’s—membrane attack complex—that bores hole in bacterial membrane

• Gram-negative bacteria more susceptible

Inflammation• Response to tissue damage from any

source (burn, cut, pathogen, other??)

• Blood vessels dilate allowing for better delivery of nutrients, O2, antibodies, complement, immune cells

• Phagocytes (monocytes and neutrophils) migrate out of capillaries--diapedesis

Fever

• Pluses• Inhibit microbial

growth• Enhance immune cell

performance• Speed tissue repair

• Minuses• Malaise• Body aches• chills

Trigger not completely understoodMuscular contraction and constriction of skin blood vessels cause core temperature to rise

“Breaking” fever or “crisis of fever”: • body begins to cool by sweating,• “color returns” as blood vessels in skin open• Indicates infection is overcome

Links to Specific Immunity

• Phagocytosis continues to be common way to kill pathogenic cells in both specific and non-specific response

• Inflammation works to allow both specific and non-specific immune response to accelerate

• Fever also allows for better performance in both specific and non-specific function

• Specific immune response and “antigen presentation” further stimulates non-specific actions like phagocytosis, complement.

Great review of “Body Defenses” or Non-specific Immunity

http://fajerpc.magnet.fsu.edu/Education/2010/2010_INDEX.HTM