Thymic selection reinterpreted.

To summarize, I have attempted to present evidence that the unselected thymocyte TCR repertoire has such a propensity to recognize MHC/peptide at high affinity that it is likely that, were tolerance induction to be invariably dominant over positive selection, all T cells would be deleted or anergized. If this is true it follows that positive selection must in fact be capable of being the dominant process. I have further suggested that the existence of peptides capable of antagonizing T-cell activation in the thymus could inhibit deletion, and that this might correspond to positive selection.