Subgroup analysis of BL-cell lines with polyclonal BL-specific antibodies

Induction of plasmacytoid and hairy cell features by phorbol esters (TPA) in B-lymphoma cells: attempted correlation with disease activity

Mononuclear cells concentrated from the blood of 16 non-Hodgkin's lymphoma (NHL) patients in the leukemic phase, were exposed to 10 ng/ml of TPA in an attempt to induce differentiation. Immunoglobulin (Ig) secretion, surface markers (SmIg, GP-70), tartrate resistant acid phosphatase (TRAP) and surface features were followed for up to six days in vitro. TPA induced 'hairy cell' like features in NHL cells as defined by cell morphology, ultrastructure, cell surface markers and the presence of TRAP. Unlike the results obtained in patients with CLL, cells from different patients at the same stage of disease reacted in a similar way. Differences were evident between NHL mononuclear cells obtained from patients in partial remission and active disease when compared with those derived from patients in complete remission. In the former group, NHL cells were maximally induced by TPA to secrete Ig and higher proportions of TRAP positive cells. In addition hairy cell features as seen by light and scanning electron microscopy were also more pronounced. TPA also induced the maximal expression of SmIg and GP-70 in cells derived from patients in this group. Patients with NHL in leukemic phase in complete remission did not express surface membrane GP-70 before or after TPA treatment while SmIg was expressed to some degree before TPA treatment and further induced following treatment with TPA. GP-70 appears to be a more reliable marker for follow-up of NHL patients than any other marker studied here.

EBV-negative and -positive Burkitt cell lines variably express receptors for B-cell activation and differentiation

The expression of receptors for proliferation and differentiation factors was analyzed by indirect immunofluorescence on 29 Burkitt lymphoma (BL) cell lines previously classified into 3 groups on the basis of their reactivity with 8 monoclonal antibodies (MAbs), including anti-CALLA, BL13 and TU1. BL13 and HB5 antibodies recognize different epitopes of the EBV/CR2 receptors. The determinant recognized by BL13 has been previously shown to be expressed only on cell lines of the first two groups, supposed to derive from the germinal center and to be negative on a third group of lines of putative BM origin and established from sporadic cases of BL. In contrast, and as expected from its reactivity on normal B cells in the BM or in the lymph nodes, HB5 antibody reacts with all BL lines except one. The receptor for transferrin is expressed on the 29 lines. Two new MAbs, Bac-1 and B1H5, could recognize respectively receptors for BCGF1 and BCGF2. Bac-1 reacts with 15 of 17 BL lines belonging to the first two groups and 7 of 12 BL lines of the third group; 14 of 15 EBV + lines express Bac-1. No BL line expresses B1H5. The IL2 receptor is weakly expressed on 5 EBV + cell lines and one EBV (-) line. All delta are BCGF1-positive. The almost constant expression of BCGF1 receptor on EBV + cell lines is the only strict relation between the expression of receptors for growth factors and their characteristics (i.e. EBV association, translocation, ethnic origin and clinical presentation). The maturation stage or the origin of BL cell lines in relation to the expression of growth factor receptors and the functional significance of these receptors will be discussed.

Expression of the mid-stage differentiation B-cell antigen GP-70 in patients with early and stable form of B-CLL

The expression of B-cell surface markers SmIg and GP-70 was determined on the mononuclear cells from the peripheral blood of 25 patients with chronic lymphocytic leukemia (CLL), 10 patients with multiple myeloma (MM), 6 normal blood donors and in 3 cases of unexplained persistent lymphocytosis. GP-70 was expressed only in CLL patients whereas multiple myeloma patients, blood donors and patients with unexplained lymphocytosis were all negative to GP-70. SmIg was expressed in CLL patients and in some of the multiple myeloma patients. Subgrouping of CLL patients to "early", stable patients (10) and to more advanced CLL patients (15) revealed differential expression of GP-70 on CLL cells from patients with more advanced stage of disease rather than in the patients with the "early" stable clinical course of disease. SmIg, on the other hand, was expressed equally on both subgroups of CLL. Furthermore, in some cases (25%) where SmIg and the light chains of Ig were only weakly expressed or were absent, GP-70 was markedly expressed. These findings suggest that GP-70 can be used as a single laboratory determination to establish clonality of the B-lymphocyte proliferation in CLL. In addition, expression of GP-70 correlates with significant clinical parameters of the disease.

Generation of a monoclonal anti-GP70 antibody and characterization of its reactivity with various human cell lines and cells from leukemia-lymphoma patients

Monoclonal anti GP-70 antibodies (BI) were generated in mice and used for screening of various malignant and non-malignant cell lines. The reactivity of these monoclonal antibodies was compared with that obtained with the polyclonal anti GP-70 antibody described in earlier studies [1-3]. The results indicated complete similarity in reactivity of both of the antibodies used. Furthermore, the reactivity of BI antibodies with cell samples obtained from a variety of leukemia and lymphoma patients and with peripheral blood samples from healthy blood donors was also very similar to the pattern of specificity described in earlier reports for the polyclonal preparation. From these studies we conclude that the monoclonal antibodies can substitute the polyclonal anti GP-70 antibodies in the diagnosis and subtyping of B-type leukemias and lymphomas.

Characterization of a novel Burkitt's lymphoma-associated antigen: GP70. Reactivity of anti-GP70 antibodies with various malignant and non-malignant cell lines

A glycoprotein of 70 kDa (GP70) was isolated from sera of Burkitt's lymphoma (BL) patients and used to immunize rabbits. Anti-GP70 antibodies at a high titer were obtained and used for screening of cancer cells of various origin by the indirect immunofluorescence test. Thus, 66% of BL-cell lines tested were positive to GP70. On the other hand, all lymphoblastoid cell lines tested were negative. Moreover, all peripheral blood cells and mononuclear cells from tonsils were negative, indicating specificity of antibodies to malignant transformation. Comparison between positively stained BL-cell lines indicated no correlation between the presence of GP70 and EBNA. Positive stain (1-5%) obtained with bone marrow cells might indicate that anti-GP70 antibodies are directed against a surface membrane differentiation glycoprotein.