A T Cell Receptor Locus Harbors a Malaria-Specific Immune Response Gene

Summary Immune response ( Ir ) genes, originally proposed by Baruj Benacerraf to explain differential antigen-specific responses in animal models, have become synonymous with the major histocompatibility complex (MHC). We discovered a non-MHC-linked Ir gene in a T cell receptor (TCR) locus that was required for CD8 + T cell responses to the Plasmodium berghei GAP50 40-48 epitope in mice expressing the MHC class I allele H-2D b . GAP50 40-48 -specific CD8 + T cell responses emerged from a very large pool of naive Vβ8.1 + precursors, which dictated susceptibility to cerebral malaria and conferred protection against recombinant Listeria monocytogenes infection. Structural analysis of a prototypical Vβ8.1 + TCR-H-2D b -GAP50 40-48 ternary complex revealed that germline-encoded complementarity-determining region 1β residues present exclusively in the Vβ8.1 segment mediated essential interactions with the GAP50 40-48 peptide. Collectively, these findings demonstrated that Vβ8.1 functioned as an Ir gene that was indispensable for immune reactivity against the malaria GAP50 40-48 epitope.