Both CD4⁺ and CD8⁺ lymphocytes participate in the IFN-γ response to filamentous hemagglutinin from Bordetella pertussis in infants, children, and adults.

Infant CD4(+) T-cell responses to bacterial infections or vaccines have been extensively studied, whereas studies on CD8(+) T-cell responses focused mainly on viral and intracellular parasite infections. Here we investigated CD8+ T-cell responses upon Bordetella pertussis infection in infants, children, and adults and pertussis vaccination in infants. Filamentous hemagglutinin-specific IFN-gamma secretion by circulating lymphocytes was blocked by anti-MHC-I or -MHC-II antibodies, suggesting that CD4(+) and CD8(+) T lymphocytes are involved in IFN-gamma production. Flow cytometry analyses confirmed that both cell types synthesized antigen-specific IFN-gamma, although CD4(+) lymphocytes were the major source of this cytokine. IFN-gamma synthesis by CD8(+) cells was CD4(+) T cell dependent, as evidenced by selective depletion experiments. Furthermore, IFN-gamma synthesis by CD4(+) cells was sometimes inhibited by CD8(+) lymphocytes, suggesting the presence of CD8(+) regulatory T cells. The role of this dual IFN-gamma secretion by CD4(+) and CD8(+) T lymphocytes in pertussis remains to be investigated.