Influenza HA specifically attenuates innate cytokines in HKSP-treated cells.
The levels of (A) IL-6, IL-23, (B) IL-12p70, (C) IL-27, (D) IL-1β, (E) IL-10 and (F) TGF-β secreted by CD14+ cells following 24 h treatment with HKSP, H1N1 HA (1μg ml-1 or 3 μg ml-1) or H3N2 HA (1μg ml-1 or 3 μg ml-1) alone or in combination with HKSP (or untreated as a control) were established by ELISA. Each column represents normalised mean cytokine levels + SEM of at least 3 experimental repeats of each treatment/donor. Each ELISA represents normalised results from multiple donors: (A) IL-6 (n = 3), IL-23 (n = 4), (B) IL-12p70 (n = 3), (C) IL-27 (n = 6), (D) IL-1β (n = 4), (E) IL-10 (n = 4), and, TGF-β (n = 3). Statistical analyses were performed to compare cytokine levels in cells exposed to HKSP versus cells exposed to H1N1 HA or H3N2 HA (1μg ml-1 or 3 μg ml-1) in combination with heat-inactivated HKSP, by fitting a One-way ANOVA to the data and using a Sidak test to adjust for multiple testing (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).