0x668143c4…385fsent to0x30cccc3d…0f29·#11,865,383·view on Etherscan
# B-cells recognize non-self only, and T-cells recognize self only
The "needle in a haystack" problem in the adaptive immune system is solved if T-cell receptors recognize non-self, and not the other way around. This also has a nice symmetry, one half of the adaptive immune system recognizes non-self, and the other half only self. Contrast. Antigen presentation to T-cells with MHC I and II is a young science. It has not been explored that long. Younger than antibodies, since those were observable more easy. And since antibodies clearly bind to non-self, there would be a priori prejudice to assume T-cell receptors did as well. Basically, every mature T-cell, if they recognize self, would have a receptor "specific" for every self-antigen in the body, because they would have passed along them all during training and their receptor would provably not react with them. So, any T-cell could activate a B-cell. This makes it scale much easier. So, T-cell receptors can either recognize 1 (one!) single antigen out of all antigen in the universe. Or, it can recognize every (every!) single self-antigen. Scalability-wise, MCH presenting cells either have to find the 1 (one!) tiny clone of T-cells that have the unique receptor for this 1 antigen out of all possible antigen. Or, they just have to find any T-cell.