Antigen receptor rearrangement and expression in acute leukemias

Twenty-two leukemias, 11 of which were undifferentiated with respect to surface antigen markers, were investigated for their antigen receptor gene rearrangement, transcription products of these antigen receptor genes, and surface antigen pattern of the cells. Among the three less-differentiated groups rearrangement was observed in 2/10 cases for the TCR beta-chain and in 4/11 cases for the heavy-chain gene. TCR beta-mRNA, however, was expressed in seven out of eight cases and the mu heavy-chain mRNA in eight out of ten cases investigated. Also mRNA of TCR alpha, the rearrangement of which could not be detected with our probes, was expressed as frequently as TCR beta. Although rearrangement of the appropriate gene was found regularly in the more mature leukemias, transcription of these genes was lower or even lacking. These findings indicate that expression of antigen receptor mRNA in undifferentiated leukemias can be activated by events other than maturational rearrangement.