The immune system recognizes a narrow range of peptide sizes (9-11 amino acids) to balance selective pathogen response with data volume.

“so you're talking about 20 to the ninth power of presentable peptide antigens and so these things are all tuned to be on the same scale this kind of scale of billions of billions in that case yeah exactly yeah so if you did it if it was like a three peptide it's it's really a small number actually there's not enough information there to you know selectively respond to a virus you know uh or a bacteria and if it was 25 peptides it's too much there's too much information there there's extra information anyway and this system i think was built to work on minimal or just the right amount of information”