FIG 3.

Immunized MHC-II KO mice do not have antigen-specific IgG antibody-secreting cell responses. In vitro production of IgG (A) and IgM (B) antibodies specific to the vaccine antigen (influenza A/PR8 VLPs). Spleen (SPL) and bone marrow (BM) cells were collected from naive B6 WT (n = 3), naive MHC-II KO (n = 3), boosted B6 WT (n = 5), and boosted MHC-II KO (n = 5) mice at day 4 after challenge with A/PR8 virus (5× LD₅₀). Media, 5-day-old in vitro cultures under medium only; PR8 VLP, 5-day-old in vitro cultures with influenza PR8 VLP vaccines coated on the plates. SPL and BM cells were plated at concentrations of 5 × 10⁵ cells/well. A/PR8 VLP-specific IgG and IgM antibodies in culture supernatants are represented by optical density readings at 450 nm. Each value represents the mean ± the standard error in quadruplicate. ns, not significant; ***, P < 0.001.