Dissecting the multifactorial causes of immunodominance in class I-restricted T cell responses to viruses

Following influenza virus infection, the numbers of mouse T-CD8+ cells responding to five different determinants vary more than 50-fold in primary responses but less so in secondary responses. Surprisingly, each determinant elicits a highly diverse and highly sensitive T-CD8+ response. Inefficient antigen processing by virus-infected cells accounts for the poor immunogenicity of just one of the subdominant determinants. Over-expressing class I-peptide complexes using vaccinia virus revealed that the poor immunogenicity of two subdominant determinants reflects limitations in T cell responses unrelated to TCR diversity or sensitivity. Despite greatly enhanced expression, the immunodominant determinant is actually less immunogenic when overexpressed by vaccinia virus. Immunodominance is also modulated by determinant-specific variations in the capacity of T-CD8+ to suppress responses to other determinants.