here we have used this assay system to show that the 300-18 murine pre-b cell line possesses a very high level of switch-recombinase activity ( greater than 1 event in 2500 cells/generation ) while a terminally differentiated , antibody-secreting hybridoma line ( a39r 1.1 ) has no detectable recombinase activity .
C0007634
cells
C1327616
secreting