Structure and Function of Basophils: Topic 1 Flashcards
what are basophils?
type of WBC that’s a granulocyte
it’s a granulocyte because it has numerous enzyme-containing specific granules within the cytoplasm
has it’s own specific granules that has unique enzymes inside compared to neutrophils and eosinophils that are also granulocytes
basophils are recognized by their dark blue/purple cytoplasmic granules
where do basophils mature?
bone marrow
Basophils comprise roughly how much of the total WBC count?
<1%
why are basophils named basophils?
Basophils are named for their abundant, large granules, which have an affinity for basic dyes and therefore stain dark blue to purple
you can’t even see the nucleus because there’s so much granulation (nucleus usually has 2-3 lobes)
what kind of granules do basophils have?
contain both specific and azurophilic granules
we usually cannot see the smaller azurophilic granules since there are so many specific granules in each cell
Basophils need to become activated in order to release their granules!!
what’s the function of basophils?
commonly involved in allergic reactions and chronic inflammation
what do the specific granules of basophils contain?
histamine = vasodilator
heparin = anticoagulant
what do the azurophilic granules of basophils contain?
lysosomal enzymes
what kind of receptors do basophils have?
Fc receptors on their surface
Fc receptors bind to the Fc portion of antibodies
what do the Fc receptors of basophils show a preference for?
IgE antibodies
what happens when a basophil is coated with IgE molecules?
When a basophil is coated with IgE molecules, antigens may bind to the Fab portion of the IgE molecules
This triggers a reaction within the basophil that causes immediate release of histamine, as well as production and release of leukotrienes (which is a slower process)
what do histamine and leukotrienes cause?
- smooth muscle contraction (particularly in the bronchial tree)
- vasodilation of the microcirculation
- increased vessel permeability
what is basophilia?
an increase in basophils
in what disease is basophilia seen?
chronic myelogenous leukemia (CML)
what is CML?
chronic myelogenous leukemia
a cancer of the bone marrow involving the proliferation of cells of myeloid lineage
usually there’s an increase in the number of neutrophils and neutrophil precursors in CML
however, it is possible for basophilia to be the sole presenting finding in the early stages of CML
basophils are derived from a myeloid precursor and since CML is a cancer of myeloid cells, it makes sense that we often see an increase in basophils in CML
