Hypersensitivity Reactions

[YouScrewedup]

I've always had trouble differentiating these.
Is there some intuitive concept that I'm missing to make it easier?

I understand that Type I: allergic reactions - mast cells, etc
Type II: antibody mediated
Type III: complex deposition
Type IV: Delayed T-Cells

But that's pretty much it. Is it just straight up memorizing the examples in FA?

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[Anti-PD1]

Type 1 is easy, think atopy

Type 2 is very specific. Antibodies target specific components. The diseases and lab findings are very characteristic, i.e. Goodpastures, Graves, MG.

Type 3 is nonspecific. Think rheumatology, deposition in serosal or joint tissues. Lots of nephritic syndromes. Even pancytopenia in lupus. Just wreckless deposition and damage. Also don't forget Arthus reaction and serum sickness. Same deal.

Type 4 is a couple of things. First, contact dermatitis which is mainly CD8 mediated, and some CD4 and dendritic cells. Then there's delayed response, like PPD and Candida sensitivity test. This is CD4 and Macrophage mediated.

When in doubt its type 3. Allegy, IgE, eosinophils its type 1. Specific reaction or effect its type 2. PPD/Candida its type 4 delayed. Nickel, poison ivy, its type 4 contact.

 

[blueforest]

Great explanation above, just wanted to give another example that I came across that might be a great test question (micro and immuno integration):

Chlamydia and pelvic inflammatory disease -> T cell mediated delayed hypersensitivity! Type IV!

 

[FindMeOnTheLinks]

Great explanation above, just wanted to give another example that I came across that might be a great test question (micro and immuno integration):

Chlamydia and pelvic inflammatory disease -> T cell mediated delayed hypersensitivity! Type IV!

Whoaaaaa that is good to know