Cells of the Immune System Flashcards
Define HSCs and their niche.
hematopoietic stem cells are the precursors to all differentiated blood cells. they are housed in the bone marrow, surrounded by osteoblasts and sinusoidal endothelial cells, as well as stromal cells that provide support and growth factors for maintenance and differentiation.
Describe where HSCs can be found and what brings them there.
- typically in the niche, called with chemical signal gradients
- released in circulation during times of stress (after differentiation) under the control of circadian rhythms
Describe hematopoietic homeostasis.
During infection, there is an increased demand for immune cells. HSCs in the bone marrow are mobilized and released to meet the demand.
What are the 2 main progenitor lineages?
- myeloid
- lymphoid
Which cells are part of myeloid lineage?
- RBCs, platelets
- granulocytes (baso, neutro, eosinophils; mast cells)
- monocyte (macrophages, DCs)
Which cells are part of the lymphoid lineage?
- NK
- T
- B (plasma
Which cytokine factors are required to produce myeloid cells?
IL-3
GM-CSF
Track the general immune response (immune cell trafficking).
- typically, naive lymphocytes are traveling in the blood looking for their antigen match.
- antigens and lymphocytes enter the lymph nodes or other lymph tissues
- APCs present the antigen to the lymphocyte here => activation to effector cell
- effector T cell will go to the infected organ (via thoracic duct => subclavian vein) and take care of the infection => memory T cells
Compare innate and adaptive immunity.
Innate - rapid - nonspecific - no memory Adaptive - specific - memory - protective
Which cell family corresponds to innate immunity? adaptive immunity?
- innate = myeloid + NK cells
- adaptive = lymphoid
Generally describe myeloid WBCs.
- most abundant
- first line of defense
- APC or phagocytic
Describe the structure of a neutrophil.
- polymorphonuclear (PMN)
- granular (neutral)
Describe the general function of a neutrophil.
“foot soldier”
- phagocytosis
- extracellular destruction of pathogen
Describe granular phagocytosis.
- pathogen binds to surface receptor
- phagocytosis into a phagosome
- acidification
- granules fuse => phagolysosome
- enzymes destroy pathogen
Differentiate between primary and secondary neutrophilic granules.
Primary = direct enzyme secondary = free radical
Describe features of a neutrophil.
- comprises 70% of myeloid WBCs
- short lived
- extracellular pathogen killing
- only enter a cell when needed, otherwise circulatory
Describe neutrophilic extracellular pathogen killing mechanisms.
- degranulation - release of granules onto a pathogen
- NET - neutrophil extracellular trap of enzymes and DNA to immobilize the pathogen
Describe the structure of a monocyte
- large
- mononuclear
- lysosomes > granules
What is the general function of a monocyte?
APC antigen processing (via phagocytosis)
Differentiate a monocyte and a macrophage.
macrophage = activated/differentiated monocyte
- monocytes are circulatory, maintain APC homeostasis, and are upregulated/recruited during infection
- macrophages are in the tissues, recognize antigens via conserved patterns, scavengers, resolve immune responses, recruit adaptive cells
Describe DC structure
long projections for increased SA for antigen display
Describe DC function.
APC
antigen processing
Describe DC features
- found subepithelial
- samples the environment via phago and pinocytosis
- informant to T cells
- migrates to lymph nodes to present to T cells
- activates adaptive immunity
Which cells interact with adaptive immunity/
macrophage
DC
Describe eos structure
- bi lobed
- granulocyte
Describe eos function
destruction of parasites via degranulation
What are major basic protein granules of eosinophils?
- toxic to parasites and surrounding tissue
- stimulates histamine inflammatory response from mast cells
What is eosinophil collagenase granules?
remodel/damage connective tissue matrix
What are leukotrienes granules of eosinophils?
- smooth muscle contraction
- increased permeability
- increased mucus secretion
What kind of reactions are eosinophils involved with?
parasitic infection
allergy
Describe mast cell structure.
- large
- mononuclear
- granules rich with histamine and heparin
Describe mast cell features
- granules => permeability, smooth muscle contraction, increased local blood flow, fluid and antibody accumulation in tissues, antigen flow in lymph
Describe local and systemic inappropriate mast cell activation.
local = hives; skin contact systemic = allergen in the blood or gut
Describe basophil structure.
- multilobed
- granules full of histamine and heparin
Describe basophil function
parasites
allergy
Where are T and B cells generated?
T = thymus B = bone marrow
Describe NK cell structure
large
mononuclear
granular
Describe NK function
kills viral infections via induced apoptosis and granules
Describe NK features
- innate
- nonspecific
- recognizes incorrect surface receptors on host cells indicating infection or tumor
What do helper T cells do?
initiate antibody formation
recruit macrophages
