Eosinophils, Basophils, Mast Cells Flashcards
Eosinophils differentiate from
myeloid progenitor, (require IL-5)
Eosinophils exits bone marrow under influence of
IL-5 and Chemokine CCL11/ Eotaxin
CCL11 is secreted by
epithelial cells and fibroblats
circulating eosinophils make up
2-5% of circulating leukocytes
half life of eosinophil
8-10 hours
eosinophila
increase in circulating eosinophils
6 steps in immune response to helminths
- activation of T cells and B cells specific for helminths (T-cells help B-cells) 2. activated B-cells differentiate to plasma cells that secrete IgE antibodies specific for helminths 3. Specific antibodies bind (via FAB region) to helminth 4. constant region (Fc-epsilon) protrudes 5.Eosinophils express Fc-epsilon-RII that bind to Fc-epsilon attached to helminth 6. Eosinophils secrete major basic protein(MBP) and eosinophil cationic protein (ECP) that are toxic to helminths
Eosinopihlia is associated with
atopic dermititis, allergies, astham whose basis is allergy
Basophils and mast cells differentiate from
myeloid progenitor
basophils mature in
bone marrow (requires IL-3)
mast cells leave bone marrow as
immature cells
mast cells enter circulation and
egress into tissues where they mature
cell surface receptors for basophils and mast cells
Fc-epsilon-RI(B2 Fc-epsilon), C3a/C4aR, C5aR(both are ligands to C3a/C4a, C5a)
receptor-ligand interactions on basophils and mast cells are
hydrophilic and hydrophobic, reversible
half life of bound IgE is
weeks to months
Half-life of IgE in serum is
2 days
half life of circulating basophils
2.5 days
circulating % of basophils
less than 1% of all leukocytes
half life of mast cells
varies with tissue compartment
activation of basophils and mast cells leads to
degranulation and histamine release and secretion of IL-4 and IL-5
during inflammation, histamine binds to
cognate receptor on endothelial cells
histamine binding during inflammation leads to
translocation of p-selectin(adhesion molecule) from the cytosol to be expressed on cell surface.
during inflammation endothelial cell vascular permeability is
increased
when IgE binds to helmith there is a
conformational change in the Fc Region binding of antigen which may explain why they can interact with Fc-epsilon receptors
Fc-epsilon-R and Fc-epsilon binding is
noncovalent and relies on ionic and hydrophobic interatcion. it is reversible.
Bound IgE antibodies are available for
binding specific for their FAB region.
when two IgE molecules of the same specificity are sufficientyl close together
the antigen binding results in crosslinking and degranulation of the basophil or mast cell. this releases histamine and other immune mediators from the granules
ligands for C3a/4aR and C5aR (C3a, C5a) following
complement activation
