Hierarchies in Cytokine Expression Profiles for Acute and Resolving Influenza Virus-Specific CD8+ T Cell Responses: Correlation of Cytokine Profile and TCR Avidity

Abstract

The development and resolution phases of influenza-specific CD8+ T cell cytokine responses to epitopes derived from the viral nucleoprotein (DbNP366) and acid polymerase (DbPA224) were characterized in C57BL/6J mice for a range of anatomical compartments in the virus-infected lung and lymphoid tissue. Lymphocyte numbers were measured by IFN-γ expression following stimulation with peptide, while the quality of the response was determined by the intensity of staining and the distribution of CD8+ T cells producing TNF-α and IL-2. Both the levels of expression and the prevalence of TNF-α+ and IL-2+ cells reflected the likely Ag load, with clear differences being identified for populations from the alveolar space vs the lung parenchyma. Irrespective of the site or time of T cell recovery, IL-2+ cells were consistently found to be a subset of the TNF-α+ population which was, in turn, contained within the IFN-γ+ set. The capacity to produce IL-2 may thus be considered to reflect maximum functional differentiation. The hierarchy in cytokine expression throughout the acute phase of the primary and secondary response tended to be DbPA224 > DbNP366. Both elution studies with the cognate tetramers and experiments measuring CD8β coreceptor dependence for peptide stimulation demonstrated the same DbPA224 > DbNP366 profile for TCR avidity. Overall, the quality of any virus-specific CD8+ T cell response appears variously determined by the avidity of the TCR-pMHC interaction, the duration and intensity of Ag stimulation characteristic of the particular tissue environment, and the availability of CD4+ T help.