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Abstract Medium conditioned by excised whole lungs from endotoxin‐injected C 57 BL mice was highly active in stimulating hemopoietic colony formation, particularly of granulocytic type, in agar cultures of mouse bone marrow cells. The colony stimulating factor (CSF) in this material had an α 1 ‐α 2 electrophoretic mobility, was eluted from calcium phosphate gel by 0.04 M phosphate buffer and had an unusually low apparent S 20 W of 1.9. Sequestered polymor‐phonuclear neutrophils were excluded as a major source of this CSF. The high specific activity and ease of preparation of lung conditioned medium make it valuable both for the large scale production of CSF and as a source of an unusual type of CSF.
Sheridan et al. (Thu,) studied this question.