Internalin B is required for mast cell–mediated innate and adaptive immune responses. (A) Purified PMCs (5 × 10⁴) from WT and α2-null mice were incubated for 1 hour with a washed suspension of WT Listeria EGD, Listeria ΔInlA (L(ΔA)), or Listeria (L(ΔB)), and anti-Listeria antibody plus or minus 50% murine serum. Supernatants were collected and assayed for IL-6 by ELISA. (B,C) WT and α2-null mice were infected for 1 or 6 hours with 5 × 10⁴Listeria (EGD), Listeria (ΔInlA), or Listeria (ΔInlB) intraperitoneally. At the indicated time points, the percentage PMN and IL-6 in the peritoneal fluid were determined. Shown is representative of 2 experiments (mean ± SEM), with each point representing 5 or 6 mice.