Innate Immune System

immunology

study of all features of the bodys second and third lines of defense, study of bodys response to infectious agents, study of allergies and cancer

a healthy functioning immune system is responsible for:

surveillance of the body, recognition of foreign material, and destruction of entities that are foreign

innate immunity (nonspecific)

inborn host defenses against a broad range of pathogens

adaptive immunity (specific immunity)

essential second tier of the immune system that targets specific pathogens to minimize their harmful effects

first line of defense

keep pathogens on the outside or neutralize them before infection begins, any barrier that blocks invasion at the portal of entry

mechanical barriers:

rinse, flush, or trap pathogens to limit their spread into the body (mucus, saliva, urine, tears)

physical barriers

structures that physically block pathogen entry (epithelial cells, tight junctions, cilia)

microbiota barrier

forms a type of structural barrier, can block the access of pathogens to epithelial surfaces

amyloid-beta protein

plays a role in innate defense of the brain by containing invading pathogens, form a mesh of fibrils that trap bacteria that are able to invade the CNS

chemical barriers

sebaceous secretions (skin, sweat)

strong acidity in the stomach

defensins

peptides that damage cell membranes and lyse bacteria and fungi

lysozyme

enzyme found in tears and saliva that hydrolyzes the peptidoglycan in the cell wall of bacteria

hematopoiesis

production of blood cells

whole blood consists of

blood cells, plasma, serum

immune cells develop from

hematopoietic stem cells in the bone marrow

white blood cells function

measure the number of leukocytes found in the blood

high white blood cell count can stem from:

bacterial infection

autoimmune disorders

drugs

low white blood cell count can stem from

viral infections or pneumonia

autoimmune diseases

severe bacterial infections

drugs

what does low neutrophil count lead to?

normal microbiota becoming opportunistic pathogens

what are the most extensive body compartments in the immune function?

reticuloendothelial system

spaces surrounding tissue cells that contain extracellular fluid

bloodstream

lymphatic system

mononuclear phagocytic (reticuloendothelial) system

continuous connective tissue framework throughout the body. activities of one compartment must be communicated to other compartments

what system is our immune system interconnected with?

the lymphatic system

what does the lymphatic system do?

collects, circulates, and filters fluid in boy tissues before its returned to the blood. surveillance, recognition, an protection against foreign materials. drains lymph fluid from extravascular tissues

describe the process of lymph

some plasma exits the capillaries, seeps into small spaces which becomes interstitial fluid, lymphatic capillaries then take this up which becomes lymph, travels to lymph nodes, screened, channeled into veins, then returns back to circulatory system

red bone marrow (primary)

found in flat bones and ends of long bones

site of blood cell production

B cells complete maturation here

Thymus (primary)

t-cell maturation

originates in the embryo as 2 lobes in the lower neck

t cells migrate and settle in the lymph nodes and spleen

secondary lymphatic organs (sites of immune cell activation, residence, and functioning)

lymph nodes

spleen

associated lymphoid tissues (MALT, SALT, GALT)

lymph node function

filters for foreign particles including cancer cells, but no detoxification function

where can lymph nodes be found?

armpit, groin, neck

spleen

leukocytes look for invaders

filters blood rather than lymph

damaged erythrocytes removed

can children have their spleen removed?

No

skin associated lymphoid tissues SALT

discrete lymphocytes beneath the skin and mucosal surfaces. effective first strike potential against influx of microbes and other foreign materials

mucosa associated lymphoid tissues MALT

tonsils: active source of lymphocytes in the pharynx

gut associated lymphoid tissue GALT

appendix

lacteals

peyers patches: compact aggregations of lymphocytes i the ileum of the small intestine

second line of defense

operates when pathogens penetrate the skin or mucous membranes

cells, antimicrobial chemicals, and processes

what kind of functions does the second line of defense provide

inflammation and phagocytosis, act rapidly at both local and systemic levels once first line has been overcome

self cells

body cells

nonself cells

any foreign material in the body

how do autoimmune disorders work?

result of the immune system attacking the bodys own tissues and organs

the immune system evaluates cells by examining molecules on cell surfaces called:

antigens or markers

consist of proteins and/or sugars

pathogen associated molecular patterns PAMPs

structures and molecules (markers) not found in or on host cells, one common PAMP is LPS which is on the outer membrane of gram-negative bacteria

pattern recognition receptors PRRs

used by host cells in the innate immunity of second line of defense

leukocytes have membrane bound or soluble proteins that recognize PAMPs

Non self proteins that are not harmful are recognized as such and the immune system is signaled not to react

what cells partake in phagocytosis

neutrophils (general purpose)

monocytes

macrophages

dendrites

Phase 1 of phagocytosis: chemotaxis

chemical attraction of phagocytes to microorganisms

step 2 of phagocytosis: adhesion

attachment of the phagocytes plasma membrane to the surface of the microbe or other foreign material

step 3 of phagocytosis: engulfment

plasma membrane of the phagocyte engulfs the microbe

step 4 of phagocytosis: phagosome formation

the microbe is surrounded with a sac called the phagosome

step 5 of phagocytosis: phagolysosome formation

phagosome and lysosome fuse to form a phagolysosome

step 6 of phagocytosis: digestion/destruction

contents of the phagolysosome brought in by ingestion are digested in the phagolysosome

step 7 of phagocytosis: excretion of residual debris

phagolysosome moves to cell boundary and excretes its waste outside the cell

inflammation

host response to tissue damage characterized by redness, pain, heat, and swelling

acute inflammation

symptoms develop rapidly and usually last for a few days or weeks (sore throat, cold, flu)

chronic inflammation

symptoms develop more slowly and can last for up to several months or years (tuberculosis, rheumatoid arthritis)

PRISH

pain, redness, immobility, swelling, heat

inflammation functions

destroy the injurious agent

limit the effects on the body by confining the agent and its by-products

repair or replace tissue damaged by the agent and its by-products

fever

universal symptom of infection

exogenous pyrogens

products of infectious agents such as viruses, bacteria, protozoans, fungi, blood, blood products, coming from outside the body

endogenous pyrogens

liberated by monocytes, neutrophils, and macrophages during phagocytosis

should you treat a slight to moderate fever (100-101)

no

high grade fever

104-106

fever side effects

tachycardia: rapid heart rate

tachypnea: elevates respiratory rate

lowering of seizure threshold

death occurs at what temperature

112-114

body temperature is maintained by the

hypothalamus

antimicrobial substances

final component of the second line of defense, proteins of the complement system, interferons, iron-binding proteins, and antimicrobial peptides

cascade reaction

sequential physiological response

first substance in a chemical series activates the next, which activates the next, and so on

classical complement pathway

initiated by binding to the antibodies that are already bound to pathogen surfaces

alternative complement pathway

initiated by the presence of foreign cell antigens, quicker response than classical pathway

lectin pathway

lectin binds to mannose on the surface of a microbe

all complement pathways have the 3 same outcomes:

opsonization: tags the invader with compliment proteins

formation of a membrane attack complex

inflammation

cytokines

signaling proteins that allow cells to communicate with each other, coordinating immune actions

cytokine storm

exaggerated cytokine response

interferons

protein molecules released by host cells to nonspecifically inhibit the spread of viral infections

type 1 (alpha and beta)

present early in infections

type 2 (gamma)

show up later in infections

produce by activated t lymphocytes

antimicrobial products: antimicrobial peptides

short proteins of 12-50 amino acids

can insert themselves into bacterial membranes