Immune System
function of the immune system
animal body is the perfect environment
immune system is made up of the cells and tissues of the body that interact with and destroy pathogens
nutrients, protection, transport
they allow the body to avoid or limit infections
molecules don't have to be pathogenic to elicit a response
immune cells release molecules into body fluids that defend the body
Innate immunity
active & passive immunity
disruptions in immune function
adaptive immunity
first line of defense
prevent pathogens from entering the body, barrier defenses
what happens when foreign substances get through
enzyme called lysozyme is antimicrobial and breaks down bacterial cell walls
secretions that trap or kill microbes also provide a defense
entry by pathogens is blocked but not impossible
skin or shell
digestive tract
airway
mucus
tears
saliva
immune system must recognize invaders
immune system needs to distinguish self from nonself
immune cells produce receptor molecules from foreign cells or viruses and activate defense
two types of molecular recognition
innate immunity
adaptive immunity
plants
vertebrates
invertebrates
lysozyme,breaks down bacterial cell walls
immune cells recognize and bid to molecules specific to viruses or microorganisms
insect exoskeleton provides a physical barrier against infection
hemocytes ingest and break down invaders using phagocytosis
double stranded viral RNA
components of bacterial and fungal cell walls
many release antimicrobial peptides that inactivate or kill bacteria or fungi
immune responses can be localized and plant wide
dead spots on a leaf
have the epidermal layer
depends heavily on signal transduction pathways
plant seals off the pathogen and kills the cells in that area
prevents the spread of disease to the rest of the plant
cellular defenses
inflammatory response
barrier defenses
lysozyme in bodily fluids destroy cell walls of pathogens
stomach provides an acidic environment kills microbes before pathogens can enter the intestines
include skin and mucus membranes
oil and sweat glands on the skin prevent bacterial growth
purpose of mucus is to trap pathogens or particles
tears
saliva
mucus secretions
phagocytic cells
natural killer cells circulate through the body and detect an array of surface proteins characteristic of virus infected an cancerous cells
toll-like receptors (TLRs) bind to the fragments of molecules on pathogens
many cellular defenses involve the lymphatic system
interferons, proteins that provide innate defense by interfering with viral infections
recognition helps trigger an immune response
TLRs improve the efficiency of phagocytosis
neutrophils, circulate in the blood and are attracted by signals from infected tissues and then engulf and destroy infecting pathogens
macrophages, large phagocytic cells
release chemicals that lead to cell death (apoptosis)
inhibits the spread of the virus or cancer
macrophages are found in the lymph nodes
limit cell-to-cell spread
some white blood cells secrete interferon that activates macrophages
virus infected body cells secrete interferon that causes nearby cells to produce substances that inhibit viral reproduction
lots of chemical signals sent out
macrophages and nuetrophils discharge signaling molecules call cytokines, some of which promote blood flow to the site
defense triggered by physical injury of infection of tissue involving the release of substances that promote swelling, enhance filtration of white blood cells, and aid in tissue repair and destruction of pathogens
mast cells found in connective tissue release histamine
histamine triggers the nearby blood vessels to dilate and become more permeable increasing redness and local blood supply
humoral immune response
cell mediated immune response
characteristics
lymphocytes form from bone marrow and circulate through the blood and lymph recognizing specific pathogens
any substance that elicits a B or T cell response is called an antigen
vertebrates only
pathogen specific recognition
T cells, mature in the thymus
B cells, mature in the bone marrow
recognition occurs when an antigen binds to a B or T cell receptor
the activation and clonal selection of plasma and memory B cells, which produce antibodies that circulate in blood and lymph
clonal selections, B cells form clones in response to a specific antigen to amplify the response the cells can have
primary immune response
activation begins when an antigen binds to a B cell receptor
secondary immune response
enhanced by cytokines, small proteins that regulate the function of other cells
one clone forms a plasma cell that produces antibodies to fight the antigen
one clone forms a memory cell that is long lasting and has receptors for the antigen
body is first exposed to a foreign antigen and a B cell is activated, producing plasma cells that make antibodies against the specific antigen
happens when the same antigen invades the body at another time; faster and greater magnitude
involves activation and clonal selection of cytotoxic T cells (Tc), which identify and destroy infected cells
activation involves T cell receptors binding to antigens displayed by antigen-presenting cells (APCs)
T cells bind to and lyse infected cells and cancer cells
pathogen enters host cell, snzymes inside cell cleave the foreign molecules into amaller peptides that can be combines with host proteins and moved to the cell surface
passive, happens when an individual receives antibodies
active, happens when being exposed to an antigen leaves circulation memory cells
result of an infection
result of vaccination
placenta to fetus
breast milk to infant
autoimmune disease
immune system avoidance
allergies
antibodies produces after first exposure to an allergen attach to receptors on mast cells
the next time, the allergen enters the body, it bonds to mast cell molecules and releases histamine and other mediators
immune system turns against specific molecules of the body allowing cytotoxic T cells to attack healthy cells belonging to self
lupus, rheumatoid arthritis, type 1 diabetes, MS
changes in epitope expression allows an antigen to avoid the immune system or the antigen goes into and inactive state
HIV escapes the immune system and attacks (infects helper T cells)