Cutting edge: Heterosubtypic influenza infection antagonizes elicitation of immunological reactivity to hemagglutinin.

A striking and selective decreases in CD4+ T-cell reactivity to the epitope following secondary influenza infection was found. Depletion of CD8+T cells prior to and throughout the duration of the secondary infection had only minor effects on the epitope-specific suppression of CD4+ T-cells after secondary infection.