Immunodominance correlates with T-cell receptor (alpha beta) gene usage in the class II-restricted response to influenza haemagglutinin.

Class II-restricted T-cell clones elicited by natural infection with influenza A virus (H3N2 subtype) exhibit extensive diversity in their recognition specificity for the envelope glycoprotein, haemagglutinin, and focus on hypervariable regions of the HA1 subunit that feature in antigenic drift. However, T-cell clones established from the same individual focus on a single antigenic site with differing fine specificity for mutant viruses. We wished to determine whether such diversity of the haplotype and contrasting immunodominance of the individual's repertoire was mirrored in T-cell receptor (TcR) gene usage. A structural analysis was undertaken of the alpha and beta chains of TcR from a panel of CD4+ T-cell memory clones established in vitro after natural infection with X31 virus and specific for eight distinct antigenic sites of the HA1 subunit: p48-67 (Ak), p58-73 (Ad), p120-139 (Ak), p177-199 (Ad), p186-200 (Ad), p226-245 (Ek), p246-265 (Ek) and p269-288 (Ak). Direct sequencing of the alpha and beta chains, using the polymerase chain reaction, revealed that T-cell clones derived from the same donor used identical V beta D beta J beta and V alpha J alpha elements. Moreover there was extensive diversity in usage of V beta (V beta 1 or V beta 4 or V beta 8) genes between individual mice, in association with diverse J beta and V alpha J alpha elements for the recognition of a common antigenic peptide. We conclude that the CD4+ T-cell memory repertoire of the individual, following primary exposure to infectious virus, is oligoclonal and recruited from a limited number of precursor cells.