Hmm, it is not exactly programming of the kind you see here. This kind of programming is genetic mode switching. Thymus is mostly random generation (unstable r

Hmm, it is not exactly programming of the kind you see here. This kind of programming is genetic mode switching. Thymus is mostly random generation (unstable regions in T cell DNA) plus filtering with inactivation of non reactive and self reactive T cells with cytokines and specific receptors. The mode switch changes T cell subtype not type of the cell based on these activation signals. (Including outright apoptosis.)