Mouse monoclonal antibodies against the idiotype of human B cell non-Hodgkin lymphomas: production, characterization and use to monitor the progress of disease

Yeast killer systems

The killer phenomenon in yeasts has been revealed to be a multicentric model for molecular biologists, virologists, phytopathologists, epidemiologists, industrial and medical microbiologists, mycologists, and pharmacologists. The surprisingly widespread occurrence of the killer phenomenon among taxonomically unrelated microorganisms, including prokaryotic and eukaryotic pathogens, has engendered a new interest in its biological significance as well as its theoretical and practical applications. The search for therapeutic opportunities by using yeast killer systems has conceptually opened new avenues for the prevention and control of life-threatening fungal diseases through the idiotypic network that is apparently exploited by the immune system in the course of natural infections. In this review, the biology, ecology, epidemiology, therapeutics, serology, and idiotypy of yeast killer systems are discussed.

Characterization of a series of isotype switch variants of a new CD20 monoclonal antibody

A series of heavy chain switch variants has been isolated from a new B cell-specific monoclonal antibody belonging in the CD20 cluster. The antibodies NKI-B20/1, NKI-B20/2b, and NKI-B20/2a (of isotype IgG1, IgG2b, and IgG2a, respectively) have been used to study the influence of isotype and of the target antigen on the capacity to mediate cytotoxicity with a number of effector mechanisms. Unlike many mouse MAbs, NKI-B20/2b and NKI-B20/2a were cytolytic with human complement on human target cells that did not express the complement regulatory factor HRF20. All 3 isotypes of NKI-B20 mediated antibody-dependent cell-mediated cytotoxicity (ADCC) with rIL-2-activated NK cells from mouse spleen. Here the antigen density seemed the most important factor in determining the level of cell kill. With mouse peritoneal macrophages as effector cells again all 3 isotypes of NKI-B20 mediated cytotoxicity. For the IgG1 and IgG2b variants of NKI-B20 this is at variance to what has been reported for MAbs of other specificities. Despite the high activity with murine effector cells none of the NKI-B20 MAbs mediated ADCC with human peripheral blood NK cells, with or without stimulation with rIL-2, due to the lack of interaction of the murine MAbs with the human Fc receptor. The CD20 antigen appears to be a good target antigen for various forms of cytotoxicity, to which its relatively high antigenic density, its resistance to antibody-induced modulation, and its unusual structure all contribute.

Enhancement of the antibody-dependent cellular cytotoxicity of human peripheral blood lymphocytes with interleukin-2 and interferon alpha

Antibody-dependent cellular cytotoxicity (ADCC) is regarded as an important mechanism by which monoclonal antibodies (mAb) can exert an antitumour effect in vivo. It may be possible, therefore, to enhance the therapeutic efficacy of mAb by cytokines that are able to enhance the ADCC of human CD3-, CD56+, CD16+ natural killer (NK) cells. We investigated in vitro the effects of recombinant interferon alpha (rIFN alpha) and recombinant interleukin 2 (rIL-2), alone or in combination, on the ADCC of human peripheral blood NK cells. Both cytokines enhanced the ADCC of the human effector cells. rIFN alpha induced a maximally increased ADCC after an exposure of human effector cells to 20 IU/ml for 15-30 min, while rIL-2 induced optimal ADCC after incubation of the cells for 2 days in 20-50 U/ml. We now show that activation of the NK cells with a combination of rIL-2 and rIFN alpha induced significantly higher levels of ADCC than either cytokine alone. The highest ADCC was induced if the cells were first exposed to rIL-2 before rIFN alpha was added to the culture. Culture of NK cells in medium or rIL-2 decreased the expression of Fc gamma RIII (CD16), indicating that intensity of CD16 expression and level of ADCC are not directly correlated, although blocking experiments with a mAb directed against CD16 showed that this Fc gamma R was essential for ADCC of the human effector cells.

Initial experience with treatment of human B cell lymphoma with anti-CD19 monoclonal antibody

Six patients with progressive B cell non-Hodgkin's lymphoma have been treated with an IgG2a mouse monoclonal antibody (mAb) against the B cell differentiation antigen CD19, with total doses varying from 225 mg to 1000 mg. Free mAb was detected in the serum after doses of 15-30 mg. After the mAb infusions the number of circulating tumour cells was temporarily reduced, but in some cases antibody-coated cells remained in the circulation for several days. mAb penetrated to extravascular tumour sites; in general higher doses were required to saturate cells in the lymph nodes than to sensitize tumour cells in the bone marrow. mAb doses of up to 250 mg were given i.v. over 4 h without major toxicity. One patient twice achieved a partial remission after two periods of mAb treatment with an 8-month interval; the second remission lasted for 9 months. One patient showed a minor response. None of the patients made antibodies against the mouse immunoglobulin. Serum immunoglobulin levels were followed as a measure of the function of the normal B cell compartment; no significant changes were seen up to 6 months after mAb treatment.

Interfaces of the yeast killer phenomenon

A new prophylactic and therapeutic antimicrobial strategy based on a specific physiological target that is effectively used by killer yeasts in their natural ecological competition is theorized. The natural system exploited is the yeast killer phenomenon previously adopted as an epidemiological marker for intraspecific differentiation of opportunistic yeasts, hyphomycetes, and bacteria. Pathogenic microorganisms (Candida albicans) may be susceptible to the activity of yeast killer toxins due to the presence of specific cell wall receptors. On the basis of the idiotypic network, we report that antiidiotypic antibodies, produced against a monoclonal antibody bearing the receptor-like idiotype, are in vivo protecting animals immunized through idiotypic vaccination and in vitro mimicking the antimicrobial activity of yeast killer toxins, thus acting as antibiotics.

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.

Therapeutic strategies for B cell malignancies involving idiotype-anti-idiotype interactions

The therapeutic use of unmodified monoclonal anti-idiotypic antibody for human B cell malignancies has met with limited success. Some factors thwarting antibody attack can be identified, such as the presence of extracellular idiotypic immunoglobulin (Ig), and the escape of the target cell by antigenic modulation. Another possibility is a change in idiotypic determinants due to somatic mutation. For direct attack on tumor cells in vivo it might be necessary to use antibody derivatives: univalent antibodies will avoid modulation, and chimeric univalent antibodies consisting of mouse Fab' gamma linked to host Ig of appropriate subclass can be engineered to mediate particular effector functions while reducing immunogenicity. Another approach is to use toxin or isotope-bearing antibodies. However, the final eradication of tumor might involve the natural non-specific, and specific anti-idiotypic mechanisms of the host which should not be damaged by antibody therapy, and which appear to be involved in control of tumor progression in patients in long-term remission. Rapidly growing animal lymphomas presently available as models cannot mimic more than a small fraction of human lymphoma but they provide useful information for design of passive anti-idiotype therapy. However host anti-idiotypic immunity must be induced in such models by pre-immunization with purified idiotype. Such a procedure can generate effective anti-idiotypic immunity which is highly protective in mouse and guinea pig lymphomas. Analysis of mechanisms involved should give insight into the role of the idiotype networks in the behavior of human disease.

Mouse monoclonal antibodies direct phagocytosis of tumor cells by human monocytes

Human peripheral blood monocytes were found to be capable of phagocytizing human B-non Hodgkin's lymphoma (NHL) cells coated with mouse monoclonal antibodies (MoAbs). The MoAbs used recognized idiotypic determinants on the surface immunoglobulin (Ig) of the tumor cells. MoAbs of IgG1 and IgG2a subclass were equally effective in inducing phagocytosis. Preincubation of the monocytes with heat aggregated Ig from human or mouse serum inhibited phagocytosis to the same degree, suggesting involvement of an Fc receptor on the monocytes that binds both human and mouse antibodies.