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Functional and structural characteristics of interleukin 2 (IL-2) receptors on B-cell chronic lymphocytic leukemia (B-CLL) cells were analyzed by a proliferation assay, IL-2 binding assay and cross-linking study. In the 3H-thymidine incorporation assay, purified B-CLL cells from four out of sixteen cases, in which the percentage of Tac antigen (Tac Ag) positive cells in peripheral blood lymphocytes ranged from 0 to 48.8%, responded to IL-2 (100 U/ml) after both 3- and 6-day incubation. No relationship was found between the responsiveness to IL-2 and the percentage of Tac Ag positive cells. In the radiolabeled IL-2 binding assay, however, B-CLL cells from all seven cases examined, including three cases with mitogenic response to IL-2 and four cases without mitogenic response, were shown to have both high- and low-affinity receptors. The number of high- and low-affinity receptors per cell ranged from 29-186 and from 420 to 1,800, respectively. Furthermore, with the affinity cross-linking method p55 (Tac Ag) and p70/75 were found even in cases without mitogenic response in their B-CLL cells. In conclusion, the B-CLL cells so far examined possessed high-affinity IL-2 receptors consisting of p55 and p70/75; nevertheless, this was not sufficient to respond to the mitogenic signal of IL-2.

Using our electron microscopic method for polysome analysis and an immunofluorescent technique we studied Ig production and secretion by tumor cells in seven BJP myeloma patients and seven "nonsecretory" myeloma patients. In BJP myeloma Ig production and secretion is of three types: Type 1, only L-chains are synthesized and secreted; Type 2, the myeloma cells show fluorescence for H-chains, but upon polysome analysis there is no peak at polysomes corresponding H-chain production; Type 3, the myeloma cells show fluorescence for H-chains, and polysome analysis shows two peaks corresponding to L- and H-chain production. Polysome analysis of "nonsecretory myelomas show the presence of only very few membrane-bound polysomes and their distribution curves are entirely different from those of "ordinary" myeloma. Furthermore, the distribution patterns vary among seven cases. Results obtained by polysome analysis and immunofluorescent technique suggest that the "nonsecretory" myeloma could be divided into several subtypes.

A case of "nonsecretory" myeloma is described. The patient had typical osteolytic lesions and marked infiltration of myeloma cells in the bone marrow, and plasma cell leukemia. A good partial remission was obtained with Melphalan, but the patient relapsed and died one year later. Immunofluorescent and immunoelectroscopic studies on the myeloma cells demonstrated the presence of cytoplasmic gamma-and kappa-chains at the initial stage and of only kappa-chains at a relapse. The electron microscopic method for polysome analysis indicated that both L-and H-chains were synthesized on membrane-bound polysomes initially, but the ability to produce H-chain was missing at the relapse.

A membrane antigen with an apparent specificity to B lymphocytes was detected with immunochemical techniques and its properties were analyzed. Anti-B-CLL serum was raised in a rabbit by immunization with B-cell chronic lymphocytic leukemia (B-CLL) cells. This anti-B-CLL serum was absorbed with erythrocytes, liver homogenate and insolubilized immunoglobulins. After further absorption with T-CLL cells, chronic myelocytic leukemia (CML) cells and acute myelocytic leukemia (AML) cells, the anti-B-CLL serum still reacted with peripheral blood B lymphocytes, B-CLL cells and hairy cell leukemia (HCL) cells. In contrast, no reactivity was seen with peripheral blood T lymphocyte or monocytes, or leukemia cells of non-B cell origin. An immunoprecipitation of radiolabeled cell surface proteins was attempted using the anti-B-CLL serum in the presence of Staphylococcus Aureus Cowan 1 (SaCl), and the precipitates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A membrane antigen with an apparent molecular weight of 76,000 daltons (P-76) was immunoprecipitated with the anti-B-CLL serum from the lysates of normal B lymphocyte, B-CLL cells and HCL cells. The antigen (P-76) is not composed of disulfide-linked subunits and has no structural relationship with HLA-DR (Ia-like) antigens or other known antigens. These results suggest that this antigen is B-lymphocyte specific, and favour the B-lymphocyte nature of HCL cells.