[Cellular regulation of the expression of i and I antigens during the in vitro differentiation of BFU-E].

Burst forming units (BFU-E) from the blood of eight normal adults were grown in methylcellulose culture. Follow up of i and I antigens detected by an indirect immunofluorescence technique from the 9th to the 14th day of culture revealed that i antigen expression diminished while maturation proceeded. On the contrary 1 antigen expression increased meanwhile. Nevertheless, in addition to this maturation process, expression of i antigen must be determined by a regulatory mechanism operating during erythroid stem cell differentiation since a large proportion of immature erythroblasts at the 10th day of culture do not express i antigen.