Tissue culture of calf bone marrow. Requirements of serum and conditioned media.

The agar culture method for growing colonies of granulocytes and macrophages from bone marrow cells has provided a technique for assaying a humoral factor, the colony-stimulating factor (CSF), which is found in plasma (1) and urine (2). This factor appears to be similar to CSF produced by feeder layers of bone marrow (3), peripheral leukocytes (4) or kidney cells (5). In general, colonies of bone marrow do not form unless this stimulant is continually present. Shad-duck and Nunna (1) found elevation of CSF in serum only during experimentally induced neutropenia, favoring the view that CSF is a humoral regulator of myelopoiesis.Although serum does not usually stimulate bone marrow colonies, Bradley, Metcalf and Robinson (6) found CSF in serum of AKR mice when leukemia developed. Bradley and Siemienowicz (7) also reported stimulation of rat bone marrow by normal rat serum. In both cases, however, fetal bovine serum was used in the culture. The question of whether normal serum can stimulate bone marrow witho...