Allergies are hyper immune response to foreign antigen.
Here we focus on immune reactions to self, bacteria and transplants.
We try to screen out self-reactive lymphocytes during development but:
- some weak interacting ones also respond to foreign antigens, so we need them
- some just escape
Paul Ehrlich discovered / described autoimmunity in early 20th century as "horror autotoxicus".
Autoimmune conditions are actually on the rise.
Central tolerance Peripheral tolerance