ABCD as Four types of hypersensivity reactions. Type I is “Allergy.”
First time you get stung by a bee – no big deal – your immune system has been sensitized
to bee venom and makes antibodies. Which is fine, if the antibodies are NOT IgE. If you’re unlucky, the second time you get
stung, you start overproducing IgE, which causes over-release histamine and other
mediators. This causes swelling and airway constriction.
So you can’t breath, unless you get a shot of adrenaline. You may remember adrenaline as “Fight or
Flight” – so it relaxes airways, providing more oxygen
to better run from tigers. So adrenaline also helps relax airways when
you’ve got an allergic reaction. Type II is Bad Blood transfusion – cytotoxicity.
If you have type B blood, but get a type A transfusion,
your body will use antibodies to kill… cells with A’s on them. Type III is “Clumps of the Arthus reaction.”
Back in 1900, Dr. Arthus injected rabbits with horse serum, and “magic clumps” formed.
Today we know those “magic clumps” are rabbit antibodies bound to foreign horse proteins. Sometimes, humans get “magic clumps” when
we only make “enough antibody” to bind to the antigen,
but “not enough antibody” to get rid of the antigen. These “magic clumps” cause problems when
they settle in joints, or in the small blood vessels in the kidney. Type IV is “Delayed” and cell mediated.
You have bad bone marrow, so you get a donor. If the donor is not well-matched to your body,
tis “bone marrow” graft will make T-cells that don’t recognize your host cells and start
attacking them. It takes time for “his T-cells” to mature
and start attacking – which is why this is a “delayed” hypersensitivity. Also, it involves big killer T-cells, NOT
small antibody proteins, so it is “Cell mediated.” Pause and review: 4 types of hypersensitivity. HelpHippo – Help support the hippocratic oath.