Peptide-pulsed C1qa^−/− DCs are poorer at eliciting IFN-γ production from naive HY-specific CD4⁺ T (Marilyn) cells. (A) Marilyn T cells were stained with CFSE and cocultured with DCs (WT or C1qa^−/−) pulsed with the HY^AbDby peptide NAGFNSNRANSSRSS. T-cell proliferation was assessed by CFSE dilution using flow cytometry. (B) WT and C1qa^−/− GM-CSF DCs pulsed with the peptide were cultured with Marilyn cells for 48 hours and supernatants tested for IFN-γ. (C) WT and C1qa^−/− splenic DCs pulsed with the peptide were cultured with Marilyn T cells for 48 hours and supernatants tested for IFN-γ. (D) WT and C1qa^−/− GM-CSF DCs pulsed with the peptide were cultured with Marilyn cells for 48 hours and supernatants tested for C1q by ELISA. One representative experiment (mean ± SD of duplicate samples) of at least 2 (splenic DCs) or 3 independent experiments performed with cells from different mice is shown. *P < .05, statistically different from control.