Anti-idiotype sera raised against surface immunoglobulin of human neoplastic lymphocytes

Ars2-containing bispecific, Fab- and IgG1-format BAR-bodies to target DLBCL cells

Despite recent advances in the therapy of diffuse large B-cell lymphoma, not otherwise specified (DLBCL), around 30% of patients develop refractory disease or relapse after first-line treatment. Recently, Ars2 was reported as the auto-antigenic target of the B-cell receptor (BCR) in approximately 25% of activated B-cell DLBCL cases. Ars2 could be used to specifically target B cells expressing Ars2-reactive BCRs. However, the optimal therapeutic format to integrate Ars2 into has yet to be determined. To mimic therapeutic antibody formats, Ars2-containing bispecific and IgG1-like constructs (BCR antigens for reverse [BAR]-bodies) were developed. Two bispecific BAR-bodies connecting single-chain antibodies against CD16 or CD3 to the BCR-binding epitope of Ars2 were constructed. Both constructs showed strong binding to U2932 cells and induced effector cell-dependent and selective cytotoxicity against U2932 cells of up to 44% at concentrations of 20 μg/ml. Additionally, IgG1-format Ars2 BAR-bodies were constructed by replacing the variable heavy- and light-chain regions of a full-length antibody with the Ars2 epitope. IgG1-format Ars2 BAR-bodies also bound selectively to U2932 and OCI-Ly3 cells and induced selective cytotoxicity of up to 60% at 10 μg/ml. In conclusion, Ars2-containing bispecific and IgG1-format BAR-bodies both are new therapeutic formats to target DLBCL cells.

The B-cell Receptor Autoantigen LRPAP1 Can Replace Variable Antibody Regions to Target Mantle Cell Lymphoma Cells

Mantle cell lymphoma (MCL) accounts for 5%–10% of all lymphomas. The disease’s genetic hallmark is the t(11; 14)(q13; q32) translocation. In younger patients, the first-line treatment is chemoimmunotherapy followed by autologous stem cell transplantation. Upon disease progression, novel and targeted agents such as the BTK inhibitor ibrutinib, the BCL-2 inhibitor venetoclax, or the combination of both are increasingly used, but even after allogeneic stem cell transplantation or CAR T-cell therapy, MCL remains incurable for most patients. Chronic antigenic stimulation of the B-cell receptor (BCR) is thought to be essential for the pathogenesis of many B-cell lymphomas. LRPAP1 has been identified as the autoantigenic BCR target in about 1/3 of all MCLs. Thus, LRPAP1 could be used to target MCL cells, however, there is currently no optimal therapeutic format to integrate LRPAP1. We have therefore integrated LRPAP1 into a concept termed BAR, for B-cell receptor antigens for reverse targeting. A bispecific BAR body was synthesized consisting of the lymphoma-BCR binding epitope of LRPAP1 and a single chain fragment targeting CD3 or CD16 to recruit/engage T or NK cells. In addition, a BAR body consisting of an IgG1 antibody and the lymphoma-BCR binding epitope of LRPAP1 replacing the variable regions was synthesized. Both BAR bodies mediated highly specific cytotoxic effects against MCL cells in a dose-dependent manner at 1–20 µg/mL. In conclusion, LRPAP1 can substitute variable antibody regions in different formats to function in a new therapeutic approach to treat MCL.

Integration of the B-Cell Receptor Antigen Neurabin-I/SAMD14 Into an Antibody Format as New Therapeutic Approach for the Treatment of Primary CNS Lymphoma

Recently, neurabin-I and SAMD14 have been described as the autoantigenic target of approximately 66% of B-cell receptors (BCRs) of primary central nervous system lymphomas (PCNSL). Neurabin-I and SAMD14 share a highly homologous SAM domain that becomes immunogenic after atypical hyper-N-glycosylation (SAMD14 at ASN339 and neurabin-I at ASN1277). This post-translational modification of neurabin-I and SAMD14 seems to lead to a chronic immune reaction with B-cell receptor activation contributing to lymphoma genesis of PCNSLs. The selective tropism of PCNSL to the CNS corresponds well to the neurabin-I and SAMD14 protein expression pattern. When conjugated to Pseudomonas Exotoxin A (ETA´), the PCNSL reactive epitope exerts cytotoxic effects on lymphoma cells expressing a SAMD14/neurabin-I reactive BCR. Thus, the reactive epitopes of SAMD14/neurabin-I might be useful to establish additional therapeutic strategies against PCNSL. To test this possibility, we integrated the PCNSL-reactive epitope of SAMD14/neurabin-I into a heavy-chain-only Fab antibody format in substitution of the variable region. Specific binding of the prokaryotically produced SAMD14/neurabin-I Fab-antibody to lymphoma cells and their internalization were determined by flow cytometry. Since no established EBV-negative PCNSL cell line exists, we used the ABC-DLBCL cell lines OCI-Ly3 and U2932, which were transfected to express a SAMD14/neurabin-I reactive BCR. The SAMD14/neurabin-I Fab antibody bound specifically to DLBCL cells expressing a BCR with reactivity to SAMD14/neurabin-I and not to unmanipulated DLBCL cell lines. Eukaryotically produced full-length IgG antibodies are well established as immunotherapy format. Therefore, the PCNSL-reactive epitope of SAMD14/neurabin-I was cloned into a full-length IgG1 format replacing the variable domains of the light and heavy chains. The IgG1-format SAMD14/neurabin-I construct was found to specifically bind to target lymphoma cells expressing a SAMD14/neurabin-I reactive B cell receptor. In addition, it induced dose-dependent relative cytotoxicity against these lymphoma cells when incubated with PBMCs. Control DLBCL cells are not affected at any tested concentration. When integrated into the Fab-format and IgG1-format, the PCNSL-reactive epitope of SAMD14/neurabin-I functions as B-cell receptor Antigen for Reverse targeting (BAR). In particular, the IgG1-format BAR-body approach represents a very attractive therapeutic format for the treatment of PCNSLs, considering its specificity against SAMD14/neurabin-I reactive BCRs and the well-known pharmacodynamic properties of IgG antibodies.

Targeting lymphoma with precision using semisynthetic anti-idiotype peptibodies

B-cell lymphomas express a functionally active and truly tumor-specific cell-surface product, the variable region of the B-cell receptor (BCR), otherwise known as idiotype. The tumor idiotype differs, however, from patient to patient, making it a technical challenge to exploit for therapy. We have developed a method of targeting idiotype by using a semisynthetic personalized therapeutic that is more practical to produce on a patient-by-patient basis than monoclonal antibodies. In this method, a small peptide with affinity for a tumor idiotype is identified by screening a library, chemically synthesized, and then affixed to the amino terminus of a premade IgG Fc protein. We demonstrate that the resultant semisynthetic anti-idiotype peptibodies kill tumor cells in vitro with specificity, trigger tumor cell phagocytosis by macrophages, and efficiently clear human lymphoma in a murine xenograft model. This method could be used to target tumor with true precision on a personalized basis.

Three major uncertainties in the antibody therapy of cancer

Antibodies against surface molecules of human tumors are now frequently administered in combination with strong chemotherapy, increasing therapeutic efficacy but making the task of elucidating immunological events more difficult. Experiments on genetically manipulated mice indicate that antibody efficacy is greatest when IgG antibody coating tumor cells is engaged by the Fcγ-receptors of effector cells, chiefly the monocyte/macrophage lineage. Evidence suggests lesser roles for NK cells, neutrophils, receptor-mediated cytotoxicity and complement-mediated cytotoxicity. The classical mode of killing employed by macrophages is phagocytosis, but much has to be learned about optimally activating macrophages for this task, and about any other modes of cytotoxicity used. There is renewed interest in antigenic modulation, which implies removal of therapeutic antibody linked with antigen from target-cell surfaces. It is now apparent that this removal of immune complexes can be achieved either by internalization by the target cell, or by transfer of the complexes to another cell by trogocytosis. In trials, anti-idiotype antibodies surprisingly proved therapeutically more effective than anti-CD20, despite anti-idiotype being more effectively removed from target-cell surfaces by antigenic modulation. This anomalous result might reflect the fact that persistence of anti-CD20 immune complexes in large amounts induces serious effector modulation, which paralyzes macrophage attacks on antibody-coated cells. The case for effector modulation is argued by analogy with the therapeutic suppression of autoimmune inflammation by effector modulation, achieved by infusion either of normal IgG in large amounts, or of anti-red cell IgG in relatively small amounts.

How well can an idiotope peptide mimic replace its parent idiotype in a synthetic peptide vaccine?

PURPOSE

To determine whether a vaccine consisting of an idiotope peptide mimic of the third complementarity-determining region of the immunoglobulin heavy chain (CDR-H3) is an effective substitute for its parent idiotype. Such peptide vaccines could ultimately be used for targeting pathological B lymphocytes.

METHODS

Hen egg lysozyme (HEL) conjugates of the Fab' fragment of monoclonal anti-fluorescein antibody 9-40 (Fab'-HEL) or a peptide mimic of the 9-40 CDR-H3 (referred to as the "B epitope" or "Bep," the conjugate is referred to as "Bep-HEL") were injected into separate cohorts of B10.A mice. Two additional control cohorts were injected with either the Bep peptide alone or a noncovalent mixture of Bep and HEL. Sera were assayed for both anti-idiotope and anti-idiotype activity by enzyme-linked immunosorbant assay (ELISA). Primary, secondary, and tertiary immune responses were examined.

RESULTS

Both the Bep-HEL idiotope and the Fab-HEL idiotype immunogens elicited homologous, allogenic immune responses. No cross-reactivity was observed between anti-idiotope and anti-idiotype responses after primary immunization. With secondary immunization, 50% of mice immunized with the Bep-HEL conjugate exhibited a cross-reactive anti-idiotype response. Conversely, 100% of mice immunized with the Fab'-HEL conjugate exhibited a marginal, but statistically significant cross-reactive anti-idiotope response. Upon tertiary immunization, 100% of mice immunized with Bep-HEL exhibited a cross-reactive anti-idiotype response, and 55.6% of mice immunized with the Fab'-HEL conjugate exhibited a cross-reactive anti-idiotope response.

CONCLUSIONS

Covalent coupling of a xenogenic carrier protein to an idiotype immunogen or its peptide mimic significantly enhances the intensity of homologous, allogenic anti-idiotype or anti-idiotope immune responses. Multiple immunizations are necessary to induce cross-reactivity between the peptide mimic and its parent idiotype.

Characterization of a human monoclonal autoantibody directed to cardiolipin/beta 2 glycoprotein I produced by chronic lymphocytic leukaemia B cells

We determined the specificity and sequence of immunoglobulin molecules synthesized by monoclonal B cells from a patient with chronic lymphocytic leukaemia (CLL) who presented with a number of clinical and biological autoimmune symptoms. Heterohybrids obtained by fusion of CLL cells with the mouse X63-Ag 8.653 myeloma produced IgM lambda MoAbs directed to the cardiolipin/beta 2 glycoprotein I (beta 2GPI) complex and ssDNA. They were devoid of polyreactivity. Nucleotide sequence analysis of the variable domain of the mu chain indicated the utilization of the VH4 71.2 gene or one allotypic variant, DXP4 and JH3 segments. The lambda light chain used the single gene from the V lambda 8 subfamily, J lambda 3 and C lambda 3 genes. The VH gene displayed 11 nucleotide changes in comparison with its putative germline counterpart. However, these nucleotide changes correspond to variations observed in other published VH4 sequences, suggesting gene polymorphism rather than somatic mutation. DXP4 and JH3 were also in germline configuration. The VL gene exhibited a single replacement mutation in CDR1. These data suggest that the monoclonal CLL B cells in this patient retained VH and VL genes in germline configuration although they secreted a pathogenic anti-cardiolipin antibody associated with clinical symptoms, vasculitis and thrombosis, which may be provoked by antibodies to the phospholipid/beta 2GPI complex.

Differentiation-linked leukemogenesis in lymphocytes

Most human lymphoid malignancies preserve a pattern of gene expression reflecting their proliferative activity and the development level of clonal expansion and maturation arrest. Characteristics of leukemia and other cancer cells frequently considered to reflect aberrant differentiation may more often reflect clonal selection of cell types that are normally infrequent and transitory. The differentiation status of progenitor or mature lymphoid cells influences which genetic elements are at risk of being exploited, via mutation, recombination, or deletion, for clonal advantage. These alterations may frequently arise spontaneously as a consequence of the unique developmental and functional programs of lymphoid cells and have as a major phenotypic consequence the stabilization of transitory cellular phenotypes.

Emergence of idiotype variants during treatment of B-cell lymphoma with anti-idiotype antibodies

We studied two patients with malignant B-cell lymphoma that manifested resistance to the therapeutic effects of anti-idiotype antibody because of the emergence of subclones with changes in their immunoglobulin idiotypes. In both patients, tumor-cell populations arose that were unreactive with anti-idiotype antibody but that retained surface immunoglobulin. One of the patients had an additional subpopulation of tumor cells that had switched from mu to gamma heavy-chain expression. Study of the immunoglobulin genes in the tumors confirmed that the subpopulations were derived from the same original clone of neoplastic B cells in each patient. The available data suggest that the idiotypic variation observed was the result of somatic mutation in the variable region of the active immunoglobulin genes. The fact that such mutations became evident over a short time and in the context of a partial tumor response suggests that the antibody therapy exerted a strong selective force against tumor cells that expressed the idiotype determinant. Multiple anti-idiotype antibodies may therefore be needed to identify all cells of a malignant clone, and some patients may require treatment with more than one monoclonal antibody.

Spontaneous alteration of idiotype in a monoclonal B-cell lymphoma. Escape from detection by anti-idiotype

The surface immunoglobulin of B-cell neoplasms provides a specific point of attack for potential antibody therapy. The capacity of anti-idiotype antibody to home to the target neoplasm requires that the idiotype be unique and that it be expressed by every cell in the neoplastic clone. We describe the evolution of an altered idiotype in a follicular lymphoma that resulted in escape from laboratory detection by monoclonal anti-idiotype antibody. This was not due to the emergence of a second (biclonal) lymphoma, since all the neoplastic cells were otherwise identical both phenotypically and genotypically, as determined by flow cytometry and genomic DNA (Southern blot) hybridization, respectively. All cells expressed the same B-cell immunotype and bore a constant amount of IgMk. The demonstration of a single configuration of immunoglobulin-gene DNA confirmed monoclonality and established that the change in idiotype was not a result of new gene rearrangements but was more likely due to somatic mutation of the variable region--a process presumed to occur naturally in B cells. These data demonstrate the lability of idiotype expression and define a mechanism by which B-cell neoplasms may become unresponsive to anti-idiotype therapy.

Acquired C1-inhibitor deficiency associated with antiidiotypic antibody to monoclonal immunoglobulins

The syndrome of acquired angioedema and C1-inhibitor deficiency is associated with B-cell lymphoproliferative disease. It is characterized by accelerated consumption of C1q and C1 inhibitor in vivo and by low levels of serum C2 and C4. Four patients with B-cell malignant diseases (IgA myeloma, macroglobulinemia, chronic lymphocytic leukemia, and B-cell lymphoma, respectively) and acquired C1-inhibitor deficiency were found to have circulating antiidiotypic antibodies to the monoclonal immunoglobulin expressed on the surface of their B cells (three patients) or in the cytoplasm of their bone-marrow cells (one patient). Two of the four patients had circulating M components, and their antiidiotypic antibodies reacted with the M components. In three patients studied the percentage of B cells bearing C1q was 18, 24, and 35 per cent, as compared with 2.3 +/- 1.7 per cent (mean +/- S.D.) in six normal controls. These results suggest that an interaction between the idiotype of monoclonal immunoglobulins and antiidiotypic antibodies causes increased consumption of C1q and C1 inhibitor in patients with acquired angioedema and C1-inhibitor deficiency. We propose that the subsequent activation of the early components of complement leads to increased vascular permeability and to angioedema and that these patients have a disease caused by antiidiotypic antibodies.

Partial characterization of bovine leukemic cell populations

Peripheral blood lymphocytes (LL) from cows with chronic lymphocytic leukemia (CLL) have been studied using a number of surface markers. Cell populations were obtained by partial enrichment and depletion using Sephadex G-200-anti-F(ab')2 and Sephadex G-200-anti-LL-Ig immunoadsorbent columns. It was shown that cell populations having different markers, i.e., surface immunoglobulins (sIg) and leukemia-associated antigens (LAA), are characterized by similar parameters. Thus the adherent cells obtained by both fractionation methods formed 1.1-4.0% of rosettes with sheep red blood cells, while 90.6-94.3% were sIg positive cells. The cytotoxicity test (CTT) performed with anti-B and anti-LL sera indicated that a vast majority of adherent cells reacted to the sera. Thus the adherent cells represent a population with a high percentage of B-cells.

Mechanisms of tumour cell escape encountered in treating lymphocytic leukaemia with anti-idiotypic antibody

Four patients with chronic lymphocytic leukaemia were treated by one or more infusions of polyclonal antibody specific for the immunoglobulin idiotype expressed on their leukaemic cells. The antibody was in the form of IgG from sheep antiserum. Three of the 4 cases showed a significant fall in blood lymphocyte count. On one occasion most of the residual circulating lymphocytes were apparently dead. However on all occasions the cell counts rebounded to near pre-infusion levels within one week. Viable lymphocytes recovered from the blood after infusion always showed evidence of antigenic modulation: a diminished level of surface idiotype in a patched distribution, with an accompanying refractoriness to lysis by anti-idiotype plus complement. When cultured in vitro blood lymphocytes from three of the four patients revealed an appreciable export of idiotypic Ig. These 3 patients showed plasma levels of idiotypic Ig up to 400 micrograms ml-1, reduced by plasma exchange prior to infusion. The fourth patient had a level of less than 4 micrograms ml-1, and was the only one in whom free antibody could be found in the plasma after infusion. These cases demonstrate two major factors which thwart antibody attack on leukaemic cells--extracellular antigen and antigenic modulation--as well as problems relating to sparseness of surface antigen, recruitment of effectors, and exhaustion of effectors.

Biological response modifiers: preclinical evaluation and clinical activity

Biological response modifiers are agents capable of affecting the host immune response toward tumors and include those biological substances produced by the human mammalian cell genome. Interferons and other lymphokines, tumor antigens, antibodies and agents which can activate or stimulate host immune responses are all included in this general category of agents. With the advent of genetic engineering and with monoclonal antibody technology, highly pure preparations of these biological substances can now be produced for tests of activity in preclinical models and in man. As the initial results accrue with highly purified preparations of interferon and with monoclonal antibodies alone or conjugated to toxic substances, the possibility of tumor specific therapy is becoming a reality. The development of preclinical models to predict for clinical activity remains a most important task to attempt to bring to clinical trials the substances most likely to be efficacious as anticancer agents. Early clinical results indicate that many of these agents can give responses in patients with clinically perceptible disease and Phase II activity studies are just beginning to define the range of clinical activity for a variety of biological response modifying agents. The development of biological response modifiers through preclinical testing and into clinical trials will be discussed in detail.

Cytotoxic effect of anti-idiotype antibody-chlorambucil conjugates against human lymphoblastoid cells

The secreted IgMs of two human lymphoblastoid cell lines, RPMI-6410 and RPMI-8392, were purified. Antisera against these two IgMs were raised in rabbits and made idiotypically specific to the respective antigens through various absorption procedures. By immunofluorescence and radioimmunoassay techniques, the purified anti-idiotype antibodies were found to react also with the membrane Igs of the respective cell lines, but not with those of other cell lines. The purified anti-idiotype antibodies were then coupled with Chlorambucil to form antibody-drug conjugates, whose effectiveness in the in-vitro killing of target cells was evaluated by a chromium-release cytotoxicity assay. The results showed that these anti-idiotype antibody-Chlorambucil conjugates were specifically cytotoxic to lymphoblastoid cells that bore membrane Igs carrying the respective idiotypic determinant(s). Furthermore, the conjugates were far more effective in causing cytolysis to the target cells than either Chlorambucil or the anti-idiotype antibodies alone.

A new method for the preparation of anti-idiotypic antibodies against six different human cold agglutinins

A method based on sequential immunoadsorption for the preparation of a highly specific antibody directed against the idiotypic determinant of human cold agglutinins (CA) is described. In the present study, human cold agglutinins (CA) were used as a model, but the method can easily be adapted for the preparation of anti-idiotypic antibodies against other monoclonal human immunoglobulins. Since regenerable immunoadsorbents were used, the isolation can be accomplished even with rather low amounts of the respective immunoglobulin.

The assessment of anti-idiopathic antibodies as effective immunoregulatory probes in vivo

In order to increase our understanding of the potential to use anti-idiotypic antibodies as immune modulators in vivo, we extensively analysed influences induced by one such antibody (anti-Id-l) following its administration to animals of different ages, genetic backgrounds, and immunological histories. Id-l is an inter-strain idiotype associated with rat anti-Group A streptococcal carbohydrate antibodies. The intraperitoneal (i.p.) injection of anti-Id-l antibodies, prepared against Id-l+ antibodies from an HPR rat could effectively induce long-term idiotype suppression in all tested strains of rats, regardless of the age at the time of treatment, the RTl haplotype or IgG2c or k-chain allotype. Total anti-streptococcal antibodies were not suppressed by this treatment. Although long-term suppression could be induced at any age, the percentage of animals suppressed following neonatal injections was consistently less than that following adult injections of anti-idiotypic antibodies. In addition, neonatal injections of anti-Id-l or Id-l with anti-Id-l appeared to enhance Id-l production in a minority of the animals. Similar treatment of adult animals never increased Id-l synthesis, suggesting that cells associated with enhanced Id-l production in older animals are either refractory to activation-differentiation signals and/or are sequestered and no longer accessible by i.v. or i.p. routes of administration of the probe. Auto-anti-Id-l immunity induced by immunizing adult rats with heavy, light, F(ab')2 fragments or whole IgG molecules could also induce an Id-l suppressed state. We were not able to induce significant Id-l suppression if animals were immunized with antigen prior to the injection of anti-Id-l. There was evidence, however, that such treatment might lead in time to the development of some idiotype specific suppression.

Cell-bound immunoglobulin on peripheral blood mononuclear cells of patients with myeloma

Four patients who had myeloma were examined for monoclonal lymphocytes in the peripheral blood using anti-idiotype antibodies. All the patients had received treatment and two were in apparent complete remission. In no case was there any evidence of peripheral blood mononuclear cells (PBMC) with endogenous surface idiotypic determinants, even in patients with active disease. It was found, however, that substantial cytophilic IgG may remain bound to Fc receptors on PBMC even after extensive incubation and washing at 37 degrees C.

Antigenic modulation of lymphocytic surface immunoglobulin yielding resistance to complement-mediated lysis. I. Characterization with syngeneic and xenogeneic complements

Following previous authors, the term antigenic modulation is used to describe the induction, by antibody, of resistance to lysis by antibody plus complement. A report is given of the rapid antigenic modulation in vitro of surface immunoglobulin (Ig) on guinea-pig L2C leukaemic lymphocytes: incubation of the cells for 2 min or longer at 37 degrees with anti-Ig diminished or removed completely the lysis occurring during subsequent incubation with anti-Ig plus complement. The modulation was effective for both xenogeneic (rabbit) and syngeneic (guinea-pig strain 2) complements, but more rapid for the latter. It appeared simply to require the action of antibody on a metabolically active cell: no requirement could be demonstrated for any serum component other than antibody, and there was a need to raise the temperature to 37 degrees after attachment of the antibody. There was molecular specificity inasmuch as modulation with anti-Ig failed to confer any resistance to lysis by another antibody (anti-Ia) plus complement.

Extracellular idiotypic immunoglobulin arising from human leukemic B lymphocytes

The peripheral blood lymphocytes of nine out of nine patients with typical surface Ig-positive chronic lymphocytic leukemia but no paraprotein visible on serum electrophoresis have been shown by radioimmunoassay to export small amounts of pentameric IgM during culture (in the range of 2.4-7.2 ng/10(7) cells per h); three out of nine also exported monomeric IgD (0.7-1.4 ng/10(7) cells per h). Immunoglobulin turned over on the cell surface did not appear to contribute to material in the culture fluid, except possibly as vesicle-bound Ig. In three cases, which included two of the IgD producers, anti-idiotypic antibody raised against the cell surface Fab mu was used to demonstrate the idiotypic nature of the exported Ig. Anti-idiotypic antibody was also used to measure levels of idiotypic Ig in the sera of these three patients as a proportion of the total Ig. Total serum IgM was depressed in all three patients, and the idiotypic IgM represented 43%, 65%, and 96% of the IgM. The findings suggest that in typical chronic lymphocytic leukemia involving B lymphocytes, the export of a small amount of idiotypic Ig by the neoplastic cells in a common or even usual occurrence.

Preliminary experience in treating lymphocytic leukaemia with antibody to immunoglobulin idiotypes on the cell surfaces

Tumour-specific antiserum was raised in sheep against idiotypic determinants on the surface immunoglobulin of neoplastic lymphocytes from a patient with chronic lymphocytic leukaemia (prolymphocytic variant). The complement-activating IgG1 subclass of the anti-idiotype was prepared from the serum in monodisperse form for infusion. Two treatments of 480 and 1200 mg caused the white-cell count to fall by one-third and one-half respectively. However, there was a rapid resurgence, so that by 8 days after each treatment the counts were restored to approximately 85% of their former levels. No change was noted in the size of spleen or lymph nodes. Each treatment probably destroyed 4-8 X 10(11) cells, some 10% of the total tumour load. The antibody was rapidly consumed, and there was evidence of heavy utilization of complement.

Idiotype-bearing peripheral blood lymphocytes in human multiple myeloma and Waldenström's macroglobulinaemia

Antisera raised against idiotypic determinants (ID) of myeloma proteins and macroglobulins have been used to differentiate peripheral blood lymphocyte (PBL) populations from individual patients. ID-positive lymphocytes not resembling plasma cells have been regularly found in peripheral blood in these diseases. For further characterization ID-positive lymphocytes were enriched from the peripheral blood by affinity chromatography using heterologous anti-idiotypic sera. Two patients with IgG myeloma, one patient with Waldenström's macroglobulinaemia and two persons with benign monoclonal hyperglobulinaemia (BMH) were examined by this technique. The ID-positive PBL population was shown to be heterogeneous with respect to non-tumour-specific surface markers, such as sheep erythrocytes (SRBC), Fc and C receptors. Tumour-specific idiotypic determinants will thus allow a more correct recognition of the total tumour cell compartment in these diseases.

Studies on the clonal origin of multiple myeloma. Use of individually specific (idiotype) antibodies to trace the oncogenic event to its earliest point of expression in B-cell differentiation

IgA myeloma proteins of kappa- and lambda-types were isolated from two patients. These were used to produce and purify anti-idiotype antibodies of both broad (myeloma-related) and narrow (individual myeloma) specificities. The anti-idiotype antibodies were conjugated with fluorochromes and used as immunofluorescent probes to trace in the patients clonal expansion at different levels of B-cell differentiation. Our results (a) confirm that B lymphocyte precursors in IgA plasma-cell myelomas are involved in the malignant process, (b) show that B lymphocytes of the malignant clone include those expressing each of the major heavy-chain isotypes, mu, delta, gamma, and alpha, and (c) provide strong circumstantial evidence that pre-B-cell members of the malignant clone are also increased in frequency. T cells expressing idiotypic determinants were not detected. These findings argue that the initial oncogenic event may occur in a B-stem cell and is not influenced through stimulation by antigen. An interesting association was the increased frequency of related clones of B lymphocytes as detected by their reactivity with anti-idiotype antibodies of broad specificity. Neither plasma cell nor pre-B-cell members of these related clones were increased in frequency. Anti-idiotype antibodies or helper T cells reactive with myeloma-related idiotypes could be responsible for this phenomenon. We discuss other implications of these findings and speculate that all of the various phenotypes of B-lineage malignancies may result from oncogenic processes affecting stem cell targets.

Antibody-induced changes in levels of cyclic adenosine monophosphate in leukaemic lymphocytes

When L2C leukaemic B lymphocytes from guinea-pigs were incubated in vitro with antibody directed to their surface immunoglobulin (Ig), a rapid rise in intracellular adenosine 3':5'-phosphate (cyclic adenosine monophosphate, cAMP) was observed. Estimation of cAMP was by a protein-binding assay using bovine adrenal protein kinase. Increases up to 30-fold occurred within 30 seconds of incubation at 37 degrees C, to be succeeded by a fall which reached the basal level between 5 and 7 min. The response was proportional to the amount of antibody present. Cross-linking of surface Ig by the antibody was necessary, bivalent (Fab'gamma)2 from the antibody gave a rise in cAMP similar to that given by the parent molecule, whereas monomeric Fab'gamma was ineffective unless it was subsequently cross-linked by anti-antibody. The rise was too rapid to have required capping of the surface Ig for its induction. Not all perturbations of the plasma membrane by antibody induce such a surge in cAMP, since anti-beta2 microglobulin, also reacting with the lymphocyte surface, failed to alter cAMP concentration. The results emphasize that immunotherapy can be influenced by antibody altering the metabolic activity of target cells, quite apart from activation of immunological cytotoxic pathways.

Lymphoblastoid cell lines from patients with chronic lymphocytic leukemia: identification of tumor origin by idiotypic analysis

Multiple lymphoblastoid cell lines have been derived from two patients with chronic lymphocytic leukemia with an associated monoclonal immunoglobulin (Ig) band. Idiotypic antisera raised against the monoclonal serum Ig bands were shown to be specific for the membrane Ig of the patients' leukemic cells. The idiotypic determinants in these patients thereby constitute tumor-specific antigens. Surface and intracellular immunofluorescence studies utilizing these idiotypic antisera were used to identify the cell lines of leukemic origin. These studies showed that certain cell lines from each patient were derived from the leukemic cells while other cell lines were derived from residual normal B lymphocytes. The leukemic cell lines were variable and contained different percentages of lymphoid cells with the idiotype-specific membrane Ig and, in addition, different percentages of plasma cells with intracellular Ig of the same specificity. Specific Ig synthesis was also demonstrated by hemagglutination-inhibition analysis of cell line supernatants. Aside from Ig specificity, no differences have been found between the leukemic cell lines and those derived from normal cells. One of the leukemic cell lines was cloned in soft agarose. All the clones were shown to be of leukemic origin.

Further studies of immunoglobulin synthesis by guinea pig leukaemic lymphocytes

The L2C leukaemia is a B-lymphocytic neoplasm of strain 2 guinea-pigs, maintained by passaging in vivo. It synthesizes mu and lambda immunoglobulin chains. These combines to form monomeric (7S) IgM molecules which are inserted into the plasma membranes. From here they are shed as monomeric IgM and as a species of higher molecular weight which has not been further defined. The synthesis of lambda chain is in excess of that required for the IgM molecule, the surplus being exported directly from the cell without any intervening phase in the plasma membrane. Quantitative estimates of synthetic rates and pool sizes for these immunoglobulin species are presented.

Rescue of immunoglobulin secretion from human neoplastic lymphoid cells by somatic cell hybridization

B leukemia cells from four different patients were hybridized with a mouse myeloma cell line with polyethylene glycol as a fusing agent. The original leukemia cells all expressed immunoglobulin on their surface, but failed to secrete it. Over 200 different human-mouse somatic cell hybrids were obtained; 57% of them secreted human immunoglobulin in large amounts. Human immunoglobulin secretion can be a stable property of these hybrid cells over months of continuous culture. In each case the human immunoglobulin secreted was restricted to the light chain type expressed by the parental B leukemia cell. In addition, these hybrid cells secreted the original mouse myeloma protein and a variety of mixed human-mouse immunoglobulin molecules.