Immunology Exam One

Immunology

the study of resistance to infection

430 BCE

observations of disease and immunity but no understanding as to why

1546

Girolamo Fracastore- basics of germ theory

Germ theory

idea that there are small microorganisms that are able to infect and make us sick

1807-1860s

growing evidence for germ theory in correlation with microscope development

late 1800’s

Koch’s postulates, identifying a microorganism as the causitive agent, early vaccinations (smallpox)

Kochs Postulates

isolate microorganism from disease host, infect healthy host, see if it causes the same disease, isolate the same microorganism

pathogens

causitive agents of a disease, some are opportunistic, a wide variety of types

late 1800s

identified many cellular and molecular components

bacteria

prokaryotic, unicellular, many extracellular, some intracellular

viruses

acellular, always intracellular (portion of life cycle)

fungi

eukaryotic, uni or multicellular, extracellular

parasites

many are helminths (worms), eukaryotic, multicellular, extracellular

protozoans

eukaryotic, uni or multicellular, extracellular

innate immunity

first and second line of defense, born with it, uses commonalities and patterns to recognize groups

innate immunity example

ability to recognize peptidoglycan in cell walls of bacteria is specific to bacteria but general to all bacteria

adaptive immunity

third line of defense, learned/developed after contact with pathogen

first line of defense

mostly physical barriers that can prevent pathogen entry

second line of defense

cells, chemicals, and processes that can immobilize or kill pathogens

humoral immunity

B lymphocytes recognize foreign antigens via B cell receptors, produce and release soluble versions (antibodies) which are released into the blood plasma

bcr’s

b cell receptors, used in adaptive immune response to recognize foreign antigens

antibody

membrane bound immunoglobulins which are secreted by b cells into the blood plasma, many types (IgG, etc) which many different effects

antigen

unique molecular shapes that can be recognized by your immune system

cell mediated immunity

t lymphocytes recognize foreign antigens using t cell receptors, need to have the antigen presented to them by antigen presenting cells using major histocompatibility complex, can differentiate into many different types of t cell effector cells

cytotoxic t cell

excrete chemicals to kill cells nearby

helper t cells

coordinate immune responses

helper t cell example

cytokines (chemical messengers)

tolerance

there is extreme diversity in molecules that the immune system can make and respond to, there are about 10^15-10^18 different molecules that the immune system could make

timeline of immune response

innate immune system works throughout infection, but especially in the first 24 hours, adaptive works 1-14 days

aspects of the first line of defense

integumentary system, respiratory tract, gastrointestinal tract, urogenital tract, microbial antagonism

skin as first line of defense

tightly packed cells, dry, acidic, secrete antimicrobial substances (fatty acids, lactic acid, defensins/peptides, lysozymes), dead cells shed regularly

mucosa as first line of defense

shed regularly (slough), mucous contains proteoglycans (protein and sugar), enzymes, and other glycoproteins which inhibit bacterial growth

microbial antagonism

microbiota compete with potential pathogens for resources

microbiota

collection of organisms which normally inhabit the body, typically do not cause disease (opportunistic pathogens are exception), are commensalistic or mutualistic, some aid in digestion

microbiota and immune development

during fetal development and after birth immune system quickly develops tolerance for these mutualistic and commensalistic species, helps secondary lymphoid tissues and mucosal barriers to develop, humans co evolved with many of these species so disruptions to this process can lead to issues such as inflammatory and autoimmune disease, allergies, diabetes, multiple sclerosis, cancer, and depression)

differentiation

cell becoming more specific, almost always a one way street, done by changing the patterns of gene expression

hematopoiesis

formation of blood cells, all differentiate from hematopoietic stem cells

hematopoietic stem cell

a common stem cell precursor which is found in bone marrow

hematopoietic stem cells split into

lymphoid or myeloid precursor

lymphoid precursor becomes

lymphocytes (b cells, t cells, nk cells)

myeloid precursor becomes

monocytes, granulocytes, megakaryocytes, erythroblasts

erythroblasts become

red blood cells (not leukocytes!)

mega karyocytes become

platelets (not leukocytes!)

granulocytes become

neutrophils, basophils, eosinophils, mast cells

granulocytes

grainy leukocytes, some are polymorphonuclear

monocytes become

macrophages, dendritic cells

leukocytes

white blood cells, nucleated, don’t carry hemoglobin

second line of defense

when pathogens breath the first line, the innate system works to limit and eliminate the infection, uses pathogen recognition (no antigen specific responses), pathogen destruction, and communicate (present) to adaptive system

pattern recognition

by soluble components of the complement system (ch 3), pattern recognition receptors detect pamps, perform phagocytosis (ch 2) and trigger inflammation

pamps

pathogen associated molecular patterns, used by pattern recognition receptors (prr’s)

inflammation

the release of inflammatory molecules or cytokines from innate immune cells, vasodilation and extravasantion, complement system proteins secreted, dendritic cells assist

vasodilation leads to

increased blood flow, decreased rate of blood flow, increased blood vessel permeability (edema)

extravasation

cells from inside blood vessel leave/exit during vasodilation, assisted by decreased blood flow rate, surface molecules triggered/expressed during inflammation, which act as anchors for monocytes and neutrophils

dendritic cells during inflammation

uptake pathogen specific antigens and migrate to secondary lymphoid tissues to interact with the adaptive immune system (eg spleen, lymph nodes, malts, galts)