At the mercy of mast cells! Beaten down by basophils, continued
5/14/08 continued: I am such a tease. Have
patience...I hardly slept last night thinking of my plight.....droopy eyelids are calling me to watch the inside of them for
a while...
5/15/08 I had my very first
set of allergy shots in my life. Obviously I needed them earlier. I had two in the left arm (dust/dustmites and
cat/dog) and one in the right (at least half a dozen molds). I get increasing doses for several months and then go to
a maintenance schedule. My body was not happy with me, essentially complaining that I was putting something I truly
don't like purposefully into myself. I have these super dark circles under my eyes that concealer can't seem to dampen.
Let's hope tomorrow is better.
Once upon a time, when I was fresh and new and was developing my immune system,
some white cells of my body that had gone to boarding school in the thymus (a gland situated on the sternum--that
bone protecting your heart) called T lymphocytes, specifically T HELPER cells and
even more specifically, the TH2 type. Want more letters and numbers? It is of the CD4+ genre. For the sake
of my sanity, I won't explain any more of this alphabet soup because as I would like to get back to the process.
Where was I? These T lymphocytes recognized an allergen (for me it was mold, dog, cat, dust, dust mites or cockroaches--one
day I will tell you about me and cockroaches because they were useful subjects for my early scientific inquiries) and released
chemicals that scientists like to call cytokines which then signaled B lymphocytes to make antibodies of the IgE type (others are IgG, IgA and IgM--more
alphabet soup, yum!) and also acted as growth factors for mast cells and activate
eosinophils.
Mast cells are widely distributed in the tissues, found mainly surrounding blood vessels and nerves.
Basophils are very similar to mast cells except they circulate through the blood stream rather than remaining in tissues.
The cytoplasm contains membrane-bound granules that contain various biologically active mediators, including histamine,
which causes the itching that allergy sufferers exhibit, as well as vasodilation (increased blood flow means increased redness),
increased vascular permeability (which allows fluids to escape and cause swelling--as with hives), bronchospasm (a sharp contraction
of the muscles of the bronchi in the lungs which makes it very difficult to breathe) and increased mucus secretion.
This is by no means an exhaustive list of the mediators and their effects, but it paints the picture. As you can imagine,
taking an antihistamine will hopefully help alleviate these symptoms.
Mast cells and basophils allow the IgE molecules to bind to their external membranes by the Fc
portion (Antibody molecules generally shaped like the letter Y. The Fc portion is the stem part of the
Y). Once enough of these accumulate on the membrane, soon they are close enough to allow an allergen to bridge across
two IgE molecules which causes the membrane to break apart and the cell degranulates, releasing all of these mediators, wreaking
havoc on the system. My dark circles are caused by that increased vascular permeability because dark circles are merely leaky
capillaries, which is what a bruise essentially is.
Eosinophils will follow up to help clean up the molecules that have been spilled
all over. Did you know that eosinophils have a diurnal variation? This
means they are more prevalent at certain times of the day, specifically in the afternoon.
Finally, to tie this into stem cells, you will
be interested to know that eosinophils and basophils, as well as the B and T lymphocytes and the other blood cells not mentioned
here, all come from a precursor stem cell in the bone marrow called an HSC,
or hematopoietic stem cell, a type of adult stem cell. Blood development is called hemopoiesis. Since one HSC
can become several different types of cells, we call it pluripotent (pluri-several,
potent-potential). A totipotent stem cell can become ANY type (total--get
it?) of cell from that organism, and can only be derived from embryonic stem cells, making these the gold standard of stem
cell work, despite the controversy of wanting to use human embryonic stem cells.
