Cells of the immune system Flashcards
Hematopoietic cells
Progenitor cells from which all differentiated blood cell types arise during the process of hematopoiesis
Where do HSCs sit in the bone marrow?
In a niche of osteoblasts or in sinusoidal endothelial cells
What is the purpose of the HSCs being in a niche?
The niche has all the growth factors and other renewal factors that are needed
Can HSCs be in the plasma?
Yes, but growth factors in the bone marrow encourage them to “home” back to the niches
HSC maintenance is also affected by what type of cell?
Stromal cells
What else do stromal cells do?
They push the HSCs toward differentiation to a certain type of progenitor cell
What two types of cells can a HSC become?
Lymphoid or myeloid progenitor
Common myeloid progenitors can become what types of cells?
Thrombocytes, red blood cells, granuloctes (e.g., mast cells), basophils, neutrophils, monocytes, or eosinophils
What can monocytes become?
Dendritic cells or tissue macrophages
Common lymphoid progenitors become what types of cells?
B cells, T cells, or NK cells
Principal cytokines for myeloid progenitors
IL-3 and GM-CSF
Principal cytokines for lymphoid progenitors
IL-7
Principal cytokines for basophils
IL-4
Principal cytokines for neutrophils
G-CSF
Principal cytokines for eosinophils
IL-5
Principal cytokines for monocytes/macrophages
GM-CSF &/or M-CSF
Principal cytokines for dendritic cells
Flt3L
Principal cytokines for B cells
Many, including IL-3 and IL-7
Principal cytokines for T cells
IL-2 and IL-7
How do activated lymphocytes get from lymph nodes into circulation?
First go through the lymph tissue to the thoracic duct, then dump into somatic circulation
What is another name for neutrophils?
Polymorphonuclear neutrophilic lymphocytes (PMNs)
What type of cell are neutrophils?
Granulated myeloid cells; not very acidic or basic
What is special about neutrophils?
They are the most abundant cell and are the “front line” in the innate immune response
What is the lifespan of a neutrophil?
Short; they usually only phagocytose once and then die
What is extracellular killing?
The neutrophils, if not large enough to phagocytose the pathogen, can release antimicrobial granules out into the mileau (which will also cause local tissue damage)
NETs
Neutrophil extracellular traps - contain the granular enzymes and killing molecules, but also DNA that immobilize pathogens
Clinical representation of neutrophil invasion
Pus
General information about macrophages
Derived from circulating monocytes
Not very granular
Highly active nucleus for constant transcription
Have a lot of lysosomes for killing
Can macrophages be antigen presenting cells?
Yes.
Describe the immune response by macrophages over the course of infection.
They are originally not large in number at the infection site, but those that are present will help with recruitment. Once recruitment takes place, the presence of T cells will help with proliferation of macrophages and their response becomes much greater.
Macrophages are strong recruiters of what process?
The inflammatory response
Primary focus of dendritic cells
Antigen presentation
Methods environmental sampling by dendritic cells
Phagocystosis or macropinocytosis
Why are dendritic cells so important?
They are the link between innate response and adaptive response; without them, there would be a very weak T cell response to any foreign invader
General features of eosinophis
Bilobed; absorb the eosin stains really well and turn bright pink. Neutralize and destroy parasitic invaders.
What is contained within eosinophils, and what does that mean for the body?
They have a lot of enzymes and molecules that cause tissue destruction, vasodilation, and inflammatory response; must be very tightly regulated by the immune system
Where are eosinophils usually found?
They are scarce, but usually reside in subepithelial connective tissue
In what are eosinophils important clinically?
The allergic response
General information about mast cells
Large, mononuclear cells that are filled with dark, basophilic granules mainly containing histamine.
What is the main job of mast cells?
To “open vascular doors;” they degranulate vasoactive substances during an infection and cause vasodilation, increased permeability
Basophils
Accomplice to mast cells and eosinophils; 2-3 lobes
Natural killer cells - appearance
Large, mononuclear cells that are distinctively granular.
Against what are NK cells aimed?
Viruses and tumor cells
Why are NK cells so important?
They are very much like lymphocytes, but they are innate so they act quickly at killing a pathogen while the adaptive immune response is “gearing up”
