Structural examination of MCs stimulated with either S pyogenes or glucose oxidase by transmission electron microscopy. MCs were incubated with medium alone (A), with S pyogenes for 6 hours (B), or with 100 mU/mL of glucose oxidase (C). Unstimulated MCs show intact nuclear membrane (A), whereas the external and internal sheets of the nuclear membrane start to separate in S pyogenes–stimulated (B) and glucose oxidase–stimulated (C) MCs. Desintegration of the nuclear membrane can be seen in panels Biii (arrows) and C. Bars are 2 μm (Ai,Bi) and 0.5 μm (Aii,Bii,iii,C).