Regulation of activin A release from murine bone marrow-derived neutrophil precursors by tumour necrosis factor-α and insulin

► Murine neutrophils contain activin A, which they spontaneously secrete in culture. ► Secretion is stimulated by TNF-α, whereas insulin blocks the response to TNF-α. ► LPS stimulates activin A release by bone marrow cells, but not isolated neutrophils. ► LPS stimulates activin A levels in the serum of TNF-α null mice. ► Neutrophils are a major source of activin A during inflammation in mice.