Surface immunoglobulin pattern of the leukaemic cell population in chronic lymphocytic leukaemia (CLL) in relation to disease activity.

The surface membrane immunoglobulin (smIg) isotype pattern of the leukemic lymphocytes was studied in 66 unselected patients with CLL. Five distinct patient groups were identified according to the dominant heavy chain isotype(s); I: smmu + (n = 22), II: smmu +/smdelta + (n = 25), III: smdelta + (n = 4), IV: smgamma + (n = 5), V: no detectable heavy chains (n = 10). The majority of group I patients had a progressive disease at test while all patients in group II were in a non-progressive state. Moreover, the smIg pattern changed with the clinical activity of the disease: when the disease progressed, the relative number of smmu + cells increased and when patients entered an indolent stage after treatment the smmu + cell population decreased. In patients with stationary disease the smIg pattern remained essentially unchanged or the relative number of smdelta + cells increased. These observations might suggest that the smIg isotype pattern of the leukemic cell population reflects the biological behaviour and the clinical activity of the disease.