Analysis of Va chain usage for the mutant D b NPN3A + CD8 + and wt D b NP 366 + CD8 + T cells by PCR with a panel of Va specific primers established that those two T cell responses indeed tend to utilise different Va chains. The wt D b NP 366 + CD8 + T cell population [36] (Day EB, unpublished) tended to use Va8 and Va17.3 (n = 3). Conversely, the D b NPN3A + CD8 + TCRs preferentially expressed Va4, Va5 and Va11 (Table S1 ). While the sample size is small and there are at least 72 different Va chains, these results provide a snapshot of the mutant D b NPN3A + and wt D b NP 366 + populations and suggest that there are differences in both Vb and Va TCR chain usage.