Immunity—non-specific/innate Overview of immune response First line of defense—barriers Second line of defense –Phagocytosis –Inflammation –Complement –Fever Relationship to specific immune response or Third line of defense

Immune Response—Overview

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

First line of Defense—physical barrier Second Line of Defense –Phagocytosis –Inflammation –Complement –Fever –All work tightly with specific immunity

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 understood Muscular 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 from innate (2 nd line) to specific/adaptive (3 rd line) 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.

Links from innate (2 nd line) to specific/adaptive (3 rd line) Immunity