Production of mouse monoclonal antibodies for the analysis of idiotypes in serum of patients with chronic lymphatic leukaemia.

In this report a simple procedure for the production of murine monoclonal antibodies (MoAb) against the idiotype of malignant B cells is described. Mice were immunized with lymphoid cells from patients with B-cell chronic lymphocytic leukaemia (B-CLL). After fusion of the spleen cells, hybridoma supernatants were screened for anti-idiotypic MoAb in ELISA with immunoglobulins obtained from tumour-cell lysates, xenohybridomas and patients' sera. The anti-idiotypic MoAb were used to study tumour cells and serum immunoglobulins (Ig) from four different patients with B-CLL. It was found that the serum IgM and IgD in one patient shared the same idiotype. Evidence is presented that IgG-secreting cell populations are not restricted to lambda-Ig-light chain-expressing B-CLL cells. With the help of anti-idiotype MoAb accurate measurements of total and idiotype-positive serum immunoglobulin levels during chemotherapy were possible.

Xenohybridization of Epstein-Barr virus-transformed cells for the production of human monoclonal antibodies.

Transformation of human B lymphocytes, obtained from hyperimmune donors with Epstein-Barr virus, yields polyclonal cell populations in which a minority of cells produce IgG antibodies of predetermined specificity, whereas the majority of cells produce 'non-specific' immunoglobulin (mainly of the IgM class). Such lymphoblastoid cell lines can be easily propagated in high-density cultures. Because cloning at 1 cell per well is not possible, stabilization of lymphoblastoid cell lines by limiting dilution is not feasible and most newly established lines cease to produce specific antibody within a few weeks. Xenohybrids, resulting from fusion of Epstein-Barr virus-transformed cells with NS1 mouse plasmacytoma cells, can be cloned at 1 cell per well. Stable xenohybridoma subclones, producing antibody of the desired specificity, can be isolated after a series of limiting dilutions. In a model system, we have studied the efficiency of xenohybridization of human lymphoblastoid cells. Using this system, we have constructed IgG anti-tetanus-toxoid- and IgG anti-HBsAg-producing cell lines. Next, we investigated whether transformation with Epstein-Barr virus is essential in such a two-step procedure or whether a polyclonal stimulator, such as pokeweed mitogen, could also be used. It was found that antibody-producing xenohybrids can be obtained after stimulation with pokeweed mitogen. However, this latter system is subject to more variations and lacks the advantage of pre-selection of antibody-producing cells as compared to xenohybridization after transformation.