In vitro medullary granulocytic progenitor (CFUc) cultures from 6 cases of granulocytopenias.

Medullary granulocyte progenitor (CFUc) cultures were grown in vitro from samples taken from 6 patients with toxic granulocytopenia caused by either thiamphenicol cephalothin or amidopyrine and who are now apparently cured. A decreased in the medullary concentration of CFUc has been observed and a calculated estimate shows that there was a decrease in their absolute number. A decrease in the number of CFUc per 10(5) metamyelocytes suggests a possible compensation by mitotic amplification between the stem cell and the differentiated cells. Two successive cultures have shown that the course of such medullary cultures is variable. The existence of medullary anomalies before drug toxicity as well as the practical consequences of the contrast between the apparent cure and the decrease in CFUc are discussed.