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: smp' (n=22), 11: smpc/sm6+ (n=25), 111: sm6+ (n=4), IV smy' (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 I1 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 smp+ cells increased and when patients entered an indolent stage after treatment the smp' cell population decreased. In patients with stationary disease the smlg pattern remained essentially unchanged or the relative number of smS+ 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.
KEY WORDS CLL SmIg Disease activity
INTRODUCTlON
Lymphoid leukaemias represent a clonal proliferation of cells which may be arrested at specific stages of differentiation . The 'classical' chronic lymphocytic leukaemia (CCL) is a heterogeneous disease including several histopathological entities . Each histological type contains subgroups which can be defined by immunological methods (Foa et al., 1979; Gordon, 1984). A number of clinical and other variables including staging systems , patterns of bone marrow infiltration (Hernandez-Nieto et af., 1977), tumour cell cytokinetics (Simonsson and Nilsson, 1980), cytogenetics (RoMrt et al., 1982) and surface glycoprotein patterns (Totterman et al., 1983) have been reported to be of prognostic significance. In addition, attempts have been made to relate immunological and functional characteristics of the CLL clone to various stages of normal lymphocyte differentiation and to the clinical course. However, the results are diverse (Foa et a/.,