Body Defenses - First Line/Innate

innate defenses

have no memory, non-specific

self-antigens

molecules considered “self” in which immune cells should ignore

auto-immune response

immune cells are activated by self-antigens

foreign antigens

immunogens, activate the immune system

Pathogen-associate molecular patterns (PAMPS)

molecular structures on pathogen surfaces

pattern recognition receptors

how immune cells recognize PAMPS

pathogen

infectious and cause disease

criteria to be a pathogen

arrive at the body surface of a host, enter the host’s body or enter a portion of the host’s body, evade defenses, multiple inside host, infect a new host

there is communication between

immune cells, normal cells and infected cells

types of innate defenses

barriers, fever, chemicals, phagocytes, natural killer cells and inflammation

types of first line of defense

skin, mucous membranes, secretions of skin and membranes, normal flora

types of second lines of defense

phagocytic cells, complement system, antimicrobial proteins, inflammation, fever

what happens in a fever

viral or bacterial infection stimulates some immune cells to proliferate and secrete proteins which raise the thermoregulatory “set point”

purpose of fever

elevated body temperature inhibits microbial growth by causing the liver and spleen to take up iron, making it not available for bacteria for their metabolism and it also increases phagocytic activity

interferons

proteins released by virus-infected cells to their neighbors

purpose of interferons

help protect cells that have not been infected, they cause cells to interfere with viral replication

complement

a group of proteins that function in innate immunity, (activation, protein cascade, response), all complement activate leads to activated C3b

classical pathway

complement proteins bind to antibody bound to antigen

lectin pathway

lectin proteins bind carbohydrates on microve surface

alternative pathway

complement protein C3 spontaneously cleaves to C3a and C3b

membrane attack complex (MAC)

protein complex from complement that attaches to membrane of the bacteria and makes holes in it (leads to lysis)

enhanced inflammation from complement

complement proteins bind to basophils and they release inflammatory mediators

neutralized viruses

C3b proteins from complement can surround a virus and neutralize their functions

opsonization

bacteria is coated by C3b proteins and can be more easily phagtocytized by macrophages

how leukocytes are involved in defenses

innate immune system cells are attracted and activated by chemical signals on the surface of pathogens

Natural killer cells

recognize infected cells and cancerous cells and induce these cells to undergo apoptosis, they are in blood and lymph

inflammation

helps maintain homeostasis

first steps of an inflammatory response

PAMPs or internal cell stress signals bind to PRRs on leukocytes, which they release inflammatory signals

systemic responses from inflammatory mediators

change in endothelial permeability, vasodilation, facilitate immune cells leaving the blood stream, recruit other immune cells to site

mast cells

immune cells that detect foreign substances in the tissue spaces and initiate local inflammatory responses against them

histamine

release by mast cells to promote vasodilation of local arterioles and permeability of capillaries

cytokines

inflammatory mediators released by macrophages

exudate

leaks from capillaries, contains fluid, clotting factors and antibodies and other proteins like complement, late swept into lymph vessels

Phagocyte mobilization steps

margination, diapedesis/extravasation, chemotaxis

margination

phagocytes enter blood from bone marrow and cling to capillary wall due to adhesion molecules in endothelial

diapedesis/extravasation

phagocytes flatten and squeeze out of capillaries

chemotaxsis

cells follow the chemical trail to injury/infection site