Such a wide variety increases the odds of having a sub-type that recognises one of the many pathogens an organism may encounter.
Too few sub-types and the pathogen can avoid the immune system, unchallenged, leading to disease.
Estimates depend on the precise type or 'compartment' of immune cells and the protein studied, but the expected billions of combinations may be an over-estimation.
[5] This can obtain thousands of DNA sequences, from different genes, quickly, at the same time, relatively cheaply.
These large-scale adaptive immune receptor repertoire sequencing (AIRR-seq) data require specialized bioinformatics pipelines to be analyzed effectively.