Medical School Pathology: Pathophysiology of Hypersensitivity

[@moshesadofsky9429]

Can I reinforce some of the points Dr. Deyrup made? Type 1 is organized around IgE (understanding that some kind of T-cell biology is tied in). Type 2 is not only antibody-mediated (all except igE), but importantly, it is Specific to the antibody target. In the kidney picture, if the antigen is a basement membrane protein, the immunofluorescence makes a SMOOTH pattern of binding. Type 3 is also antibody mediated, but the specificity is not so important. A complex of antibodies and antigens forms in solution, and gets stuck for structural reasons, leading to accidental damage wherever it gets stuck. So bumpy deposits in the kidney, or scattered vasculitis, or skin lesions. And type 4 is "everything else", mostly T-cell mediated. I read a fascinating paper about the Type 1 reaction. If you inhale an antigen, say pollen, how does the immediate hypersensitivity work? The antigen is in the airspace. The mast cells are pretty deep - not touching the airspace. The important new information is that antigen presenting cells do reach into the airspace, gather antigens on their surface, and make little blebs of membrane delivered to the mast cells inside. Boom!

[@PathologyCentral]

You're such an amazing educator, Dr. Sadofsky! Thank you for your comment!