Continuing our conversation on hypersensitivities, we’re moving on to number II today! Do you say number II when you do Roman Numerals? Is Roman Numerals supposed to be capitalized? None of these questions will be addressed in this week’s article!
Type II gets kicked off by autoantibodies, meaning antibodies to self tissue. For this reason, we also call it “antibody-mediated.” These are generally going to be IgM or IgG, as opposed to the IgE used in type I. The antibodies are really just getting confused and seeing our own cells as something foreign, needing to be destroyed. This destruction usually happens via the Membrane Attack Complex (MAC).
We also split type II reactions into cytotoxic and non-cytoxic. Cytotoxic are the ones that destroy the cell, like we just talked about. They fix complement and do all those things. Non-cytotoxic bind and interfere with normal function. These are usually binding to a receptor of some kind, which some organizations are recategorizing to a new Type V Hypersensitivity.
Common examples of Type II are Rheumatic fever and Pemphigus vulgaris. You can also put Myasthenia gravis and Graves disease in here, but remember that those are receptor specific. So some will list them under the Type V category.
Not too bad when we break it down, right? Next week, onto type III!