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immunology
the branch of biomedical science that studies resistance to infection and mechanisms used by organisms to defend themselves against microorganisms or foreign particles
opportunistic pathogens
pathogens that cause disease only when the immune system is not functioning properly or enters a site where it can grow uncontrollably
extracellular pathogens
microorganisms that cause disease by growing and replicating outside host cells, in bodily fluids or tissues. They include bacteria, fungi, and some parasite
intracellular pathogens
microorganisms that invade and replicate inside host cells like viruses
tolerance
inactivation of immune response to self; occurs during B and T cell development and in other ways throughout the body
hematopoietic stem cells
stem cells that differentiate into progenitor cells for a specific cell line
myeloid progenitor cells
cells that give rise to most cells involved in innate immunity and antigen presentation
monocytes
cells that can differentiate into macrophages and dendritic cells
lymphoid progenitor cells
cells that give rise to innate lymphoid cells (ILC) and natural killer (NK) cells
innate lymphoid cells
a group of immune cells that provide rapid, non-specific responses to infections and tissue damage by producing cytokines and regulating information
granulocytes
a type of leukocyte that contains granules within the cytoplasm that can degrade the pathogen: neutrophils, eosinophils, basophils, and mast cells
agranulocytes
a type of leukocyte that do not contain granules: monocytes and lymphocytes
peptidoglycan
a complex structure made of sugars and amino acids which provide structural support to bacterial cell walls
bacterial capsule
a protective layer composed primarily of polysaccharides that surround the cell wall
virus
an infective agent that typically consists of a nucleic aid molecule in a protein coat
enveloped viruses
these viruses have a nucelocapsid enclosed in a lipid membrane known as the envelope; they are easily disrupted by changes in the environment because the membrane is very fragile
nonenveloped viruses
a type of virus that lacks a lipid bilayer envelope; more resistant to changes in the environment
fever
a byproduct of inflammation that causes a rise in temperature which lowers the rate of replication of many pathogens and increases the activity of the adaptive immune system
primary lymphoid tissues
the sites where lymphocytes develop and mature: bone marrow and thymus
secondary lymphoid tissue
sites where the antigen from pathogens is presented by APC and lymphocytes are activated: lymph nodes, spleen, tonsils, MALT
lymph nodes
part of the lymphatic system of vessels that drain extracellular fluid lymph from tissues to blood; a connection between circulatory and lymphatic systems
spleen
an organ that activates T cells and B cells circulating through the blood
allergies
a malfunction of the immune system in which granulocytes recognize innocuous material as foreign —> activating granulocytes and induces localized symptoms to expel the antigen
immunodeficiency
a lack of immune system function where immune cells cannot mount the proper response producing a higher likelihood of pathogen infection
cancer
occurs when individuals acquire random mutations in genes controlling cell division and if the immune system fails the eliminate them, cells may grow uncontrollably
PAMPs
molecules that are characteristic of a broad range of microbes that are not normally present in the body: lipopolysaccharides, mannose, bacterial or viral DNA, flagellin, microtubules, peptidoglycan and lipo-teichoic acid
toll like receptors
transmembrane proteins on the surface of cells like dendritic cells and macrophages that recognize a variety of PAMPs
lectin receptors
a type of receptor that binds to carbohydrates common to pathogen cell surfaces like polysaccharides or sulfates sugars. Binding to these receptors activates phagocytosis
scavenger receptors
SR-A and SR-B on macrophages bind to negatively charged ligands such as sulfated sugars, lipo-teichoic acid, and lipopolysaccharides
cytosolic innate receptors
RIG-1 and NOD-like; a type of receptor that recognizes intracellular sytosolic PAMPs such as viral nucleic acids and bacterial signaling molecules. They activate cells responses that inhibit growth of intracellular pathogens and recruit white blood cells to destroy the infected cell
opsonin receptors
Fc receptors and CR1, CR3, and CR4 complement receptors; immune cell receptions that recognize molecules like antibodies and complement proteins (Cb3 and C4b) that coat pathogens to enhance phagocytosis
cytokines
secreted proteins that have signaling roles in the immune response like TNF-a and IL-1
antiviral cytokines
a family of secreted proteins that include IL-12, IFN-a, and IFN-B that activate natural killer cells to find and destroy virus infected cells
chemokine
a type of cytokine that acts as a chemoattractant for immune cells
TNF a
a cytokine produced by macrophages that induces fever and vascular permeability
IL-6
a cytokine produced by macrophages that induces fever and activates liver cells to produce acute phase response proteins
CXCL8
a chemokine produced by macrophages that attracts neutrophils and basophils
IL-12
a cytokine produced by macrophages that recruits and activates NK cells
caspase 1
an enzyme present in inflammasomes that cleaves cytokines into their active forms
neutrophils
fast-acting innate immune granulocytes that engulf pathogens, release antimicrobial enzymes, and form extracellular traps to fight infections; they are more mobile that macrophages and comprise 50% of circulation of white blood cells
glycoproteins
proteins on neutrophil surfaces that bind to selectins on vascular endothelial cell surfaces
integrin
a protein on neutrophil cell surfaces that bind to ICAM on vascular endothelial cell surfaces
IFN y
a cytokine released by activated NK cells to recruit cytotoxic T cells to the dendritic cells so they can recognize the antigen the DC is presenting
Class I MHC
the class of MHC that presents peptides from degradation of intracellular proteins and binds to CD8 co-receptor
class II MHC
class of MHC that presents peptides from external pathogens degraded in lysosomes and binds to CD4 co-receptors on CD4+ T cells
immunoglobulins
B cells receptors that recognize antigens at the surface of B cells or soluble antigens through the production of antibodies
thymus
where T cells mature
bone marrow
where both B and T cells are produced but only B cells mature here
isotope switching
a process in which the constant region of the antibody’s heavy chain is altered, changing its functional properties but not antigen binding
