Immunogenicity Threshold in Allogeneic Cells Impacts CTL Response to Nondominant Congenic Antigens

Transplantation and cancer expose the immune system to neoantigens, including immunogenic (dominant and subdominant) and nonimmunogenic Ags with varying quantities and affinities of immunodominant peptides. Conceptually, immunity is believed to mainly target dominant Ags when subdominant or nondominant Ags are linked within the same cell due to T cell interference. This phenomenon is called immunodominance. However, our previous study in mice showed that linked nonimmunogenic Ags (OVA and GFP) containing immunodominant peptides mount immunity irrespective of the MHC-matched allogeneic cell's immunogenicity. Consequently, we further explored 1) under what circumstances does the congenic marker CD45.1 provoke immunity in CD45.2 mice, and 2) whether linking two dominant or subdominant Ags can instigate an immune response. Our observations showed that CD45.1 (or CD45.2), when connected to low-immunogenic cell types is presented as an immunogen, which contrasts with its outcome when linked to high-immunogenic cell types. Moreover, we found that both dominant and subdominant Ags are presented as immunogens when linked in environments with lower immunogenic thresholds. These findings challenge the existing perception that immunity is predominantly elicited against dominant Ags when linked to subdominant or nondominant Ags. This study takes a fundamental step toward understanding the nuanced relationship between immunogenic and nonimmunogenic Ags, potentially opening new avenues for comprehending cancer immunoediting and enhancing the conversion of cold tumors with low immunogenicity into responsive hot tumors.