Interleukin-1β Response of Peritoneal Macrophages to Streptococcus pyogenes Exposure: Differential Response to Living and Heat-killed Bacteria

BackgroundA human CD46-transgenic (hCD46-Tg) mouse model of subcutaneous infection into hind footpads has been established with group A streptococcus (GAS) isolates, and hCD46 has been found to enhance progression of necrotizing fasciitis in the feet.MethodsTo clarify immune responses and host cell death in streptococcal toxic shock syndrome (STSS), we determined the responses [release of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6] of peritoneal macrophages extracted from hCD46-Tg mice at 24 hours after exposure to GAS472, a STSS-derived strain. Variations of hCD46 expression in cells from the popliteal lymph nodes were examined 24–72 hours after GAS472 infection.ResultsMacrophages exposed to GAS472, but not heat-killed bacteria, exhibited releases of IL-1β, TNF-α, and IL-6. Percentage of hCD46-expressing cells was decreased 72 hours after infection.ConclusionThese preliminary findings suggest that the macrophages exposed to GAS472 may induce proinflammatory cytokine expression including of IL-1β, TNF-α, and IL-6 and consequent cell death after infection in mice.