Human T-cell clones recognize chemically synthesized peptides of influenza haemagglutinin

The continual variation in the antigenic structure of the haemagglutinin (HA) molecule is associated with the appearance of new epidemics or pandemics of influenza in immune populations1. The detailed analysis of HA structure has provided the molecular basis of this phenomenon2–4and while four antibody-binding sites have been suggested4, the epitopes of HA that are recognized by T cells remain undefined. Using chemically synthesized peptides corresponding to sequences of the HA molecule5, we have investigated the antigenic determinants recognized by long-term T-lymphocyte lines and clones induced with HA and maintained in T-cell growth factor (TCGF or interleukin-2, IL-2). The data suggest that HA-specific T-cell populations contain the repertoire to respond to all the synthetic peptides analysed. However, when responses are analysed at the clonal level, one peptide located at the carboxy-terminus of the HA1 molecule and discrete from the proposed antibody-binding sites4seems to be immunodominant.