The expression of FMC-7 appears to be maturation linked. Upon stimulation of B cells in vivo the expression of the molecule increases. The B cells that get involved in antibody production loose the marker, but in peripheral blood approximately 50% of the B cells carrier the antigen. Expression of the FMC-7 epitope is used to distinguish different types of B cell leukemia's. The antibody aides to the differentiation between PLL and B-CLL, but it is also useful in confirmation of the diagnosis of other disorders such as SLVL, HCL, and HCL-V. During and after treatment the antibody can help monitoring the effect of therapy in these diseases.