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)