Although IL-1ß secretion by these cells was considerably less than by THP-1 macrophages, it was clearly induced by infection with B. infantis. As in the THP-1 cells, B. infantis-induced IL-1ß secretion by primary human MDMs was not affected by heat killing the bacteria or by inhibiting phagocytosis with cytochalasin D, but was almost completely inhibited by raising the levels of extracellular potassium (Fig 6A). Here, IL1B is linked to infection.