The immunodominant CD4 epitope GP 67–80 within LCMV GPV generated anti-LCMV CD4 T cells (Fig. 1B), those virus-specific CD4 T cells failed to help the few (5%) LCMV-specific GP CD8 CTLs present in the spleens of GPV-infected mice to cause T1D. Here, CD8A is linked to type 1 diabetes mellitus.