Hypersensitivity Reactions Best way to memorize types 1-4 for Medical Boards
Hypersensitivity reactions and how I know them
There are 4 types of hypersensitivity reactions. Here is an easy way to remember which category is each one.
I’m going to start with Type 3 because I’m just so excited about it.
Type 3 reaction has to do with antigen-antibody complex. To remember what diseases are type 3 just remember this sentence: “King Arthur, Peter PAN, and a Werewolf… these THREE always fighting make sick! PS this is type 3” King Arthur should remind you of Arthus reaction which is swelling and inflammation following tetanus vaccine. The PAN in Peter Pan should remind you of Polyarteritis nodosa. The werewolf should remind you of Lupus, because Lupus in Latin is wolf. Sick stands for serum sickness. The “PS” at the end is to remind you of Post-Streptococcal Glomerulonephritis. So if you can picture this in your head you will never forget what type of reaction these ones are.
Type 1 means it is an immediate, fast type of anaphylaxis. It is antibody mediated that can be tested on skin looking for IgE. The free antigen cross linking causes mast cells and basophils to release vasoactive amines such as histamine that act at postcapillary venules. So for this first one think of anything that happens right away such as bee stings and food allergies, as well as atopic disorders such as hay fever, rhinitis, hives, and asthma.
Type 2 is cytotoxic where the antibody and complement lead to the membrane attack complex known as MAC. There are a lot of examples of type 2 reactions, but I will save the laundry list till the end because it is easier to just remember what is in the other categories and then just say everything else is type 2.
Type 4 hypersensitivity reaction is delayed and does not involve antibodies. These ones are cell-mediated and therefore it is not transferable by serum. Sensitized T cells encounter antigen and then release cytokines which leads to macrophage activation. Because these are T-cell mediated just remember the T’s for these diseases: Transplant rejections such as Graft vs host, TB skin test, and Touching such as contact dermatitis. Also random is multiple sclerosis.
So to sum it all up:
Hypersensitivity is a set of undesirable reactions produced by the normal immune system, including allergies.
Type 1: Anaphylactic and atopic fast reactions.
Type 2 : Cytotoxic antibody mediated including everything not previously mentioned. Type 2’s include Bullous pemphigoid, goodpasture syndrome, Graves disease, Guillan-Barre syndrome, Myasthenia Gravis, Pernicious anemia, and Rheumatic fever.
Type 3: “King Arthur, Peter PAN, and a Werewolf… these THREE always fighting make sick! PS this is type 3” That’s for Arthus reaction, Lupus, Polyarteritis Nodosa, Poststrep- GN, and Serum sickness.
Type 4: The T’s: TB tests, transfers, and touching aka contact dermatitis such as poison ivy. Don’t forget about Multiple sclerosis which is a random type 4 reaction.
Hope this helps.
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