Importance of antibody isotype in monoclonal anti-idiotype therapy of a murine B cell lymphoma. A study of hybridoma class switch variants

An initial panel of four syngeneic monoclonal antibodies directed against the idiotype of a murine B cell lymphoma was used to treat this tumor in vivo. The antibody in the panel of the IgG2a isotype was more effective in treatment than the other antibodies, which were of the IgG1 and IgG2b isotypes. To independently assess the role of antibody isotype in mediating antitumor effects, switch variant hybridoma families were isolated from the hybridomas secreting the less effective IgG1 and IgG2b antibodies. A family isolated from an IgG1-secreting parent consisted of IgG1-, IgG2b-, and IgG2a-secreting members, and an IgG2a variant was isolated from an IgG2b-secreting parent for another family. Antibody members of each family differed only in heavy chain composition and were the same with respect to their light chains and their affinity and specificity for idiotype. The IgG2a members of both families were superior to the other members in inhibiting tumor growth with an order of effectiveness of IgG2a greater than IgG1 greater than IgG2b. These in vivo results paralleled the abilities of these different isotype antibodies to mediate antibody-dependent cellular cytolysis in vitro. For the IgG2b----IgG2a family, in vivo treatment with the IgG2a member given i.p. after i.p. tumor challenge at one-tenth the dose of the IgG2b member was still superior to the latter. At one-hundredth the dose of the IgG2b, the IgG2a was still superior to the latter when the antibodies were given i.p. and tumors subcutaneously. These data and those showing that the clearance of these antibodies from the serum differed in only a relatively minor way indicate that the IgG2a antibodies in this system had greater antitumor effects primarily by virtue of their greater capacity for host effector interaction.

A clinical trial of anti-idiotype therapy for B cell malignancy

Eleven patients with B lymphocytic malignancy were treated with mouse monoclonal anti-idiotype antibodies. All but one of the patients in this study had received extensive prior treatment with conventional lymphoma therapy. All antibodies were prepared against, and uniquely reactive with, the patient's own tumor. Ten patients were treated with a single antibody, but one patient received three antibodies concurrently. The treatment protocol initially used an escalating dose schedule that was intended to evaluate toxicity, pharmacokinetics and, eventually, to achieve appreciable levels of free mouse antibody in the circulation. The last two patients received substantial initial doses. Tumor sampling was performed before and during therapy to evaluate tissue penetration by antibody. None of the patients had serum paraproteins by routine clinical testing, but six had idiotype protein detectable by a sensitive immunoassay at levels greater than 1 microgram/mL, two of which were greater than 200 micrograms/mL. Plasmapheresis was capable of reducing these levels temporarily. However, the presence of serum idiotype increased the requirement for mouse antibody to achieve tumor penetration. Another obstacle to treatment was immune response to mouse Ig, which occurred in five of the 11 patients. Once an immune response had begun, further infusions of antibody were not capable of reaching the tumor or inducing tumor regression and were associated with toxicity. Our initial patient remains in an unmaintained complete remission 42 months after receiving antibody. Five of ten additional patients have had objective remissions that were also clinically significant. However, these remissions were not complete and were of relatively short duration. This therapy shows promise as an alternative modality for the treatment of B cell malignancy. Further study will be needed to determine the mechanisms of the antitumor effect and to improve the clinical results.

Monoclonal anti-idiotype antibodies against the murine B cell lymphoma 38C13: characterization and use as probes for the biology of the tumor in vivo and in vitro

To establish a murine model for the monoclonal anti-idiotype immunotherapy of B cell lymphoma, a panel of rat and murine monoclonal anti-idiotype antibodies of several different isotypes was generated against the surface immunoglobulin of the murine B cell tumor 38C13 (38C). Xenogeneic antibodies were made from fusions of rat spleen cells immunized with the 38C idiotype. Syngeneic monoclonal anti-idiotypes were generated from mice immunized with the idiotype conjugated to the protein carrier KLH. Small differences were noted in the ability of the antibodies to cross-block one another, but all appeared to be directed against the same or closely spaced idiotopes on the immunoglobulin molecule. The antibodies selectively precipitated surface Ig from 38C tumor cells and not from normal mouse spleen cells. They were used to selectively stain 38C tumor cells in cell suspensions for FACS analysis or immunohistochemical staining of tissue sections from mice bearing the tumor. As the malignancy progressed, the number of tumor cells found in all tissues examined increased. Thus, the anti-Id antibodies provided a specific probe for tumor cell detection. The antibodies had no detectable effect on cell growth in vitro; however, they did cause the rapid transient loss of the expression of cell surface Ig. This modulation was concentration and time dependent but not 100% complete. Re-expression of the Id occurred by 24 h following removal of the anti-Id antibodies. When these antibodies were used in sensitive radioisotope and enzyme linked immunoassays, the tumor cells were found to secrete small amounts of idiotype in vitro and in vivo. The level of idiotype detected in vivo correlated with tumor growth and inversely with survival. This work is an attempt to develop further an animal model system in which to test the diagnostic and therapeutic effects of monoclonal anti-idiotype antibodies.

Strategies for production of monoclonal anti-idiotype antibodies against human B cell lymphomas

Murine monoclonal antibodies (MAB) against the idiotype (Id) of B lymphocyte malignancies are powerful reagents for the study of these diseases, and are potentially useful for treatment. Different strategies for the production of these anti-Id MAB have been compared. Initially, the Id Ig from nonsecreting B cell tumors was "rescued" by human X mouse or human X human hybridization. These somatic cell hybridizations resulted in the secretion of human Ig in 10 and 100% of the fusions, respectively. In a second step, anti-Id MAB were produced by using the "rescued" Id Ig as immunogen. A more streamlined approach is based on a one-step procedure in which the tumor cell suspension is used as immunogen. This method of immunization, coupled with a four-layer ELISA, results in the detection of anti-Id MAB in a frequency of approximately 1% of the total hybrids. By using a pool of 10 different anti-Id MAB, each reactive with the tumor of one patient, we searched for idiotypic relatedness among a panel of 50 additional tumors. No cross-reactions were found, indicating that our current strategy results in the identification of unique idiotypic determinants among human B cell tumors. Idiotypic Ig can be found in the serum of patients with B cell tumors. Among groups of patients, there is a wide spectrum of serum Id levels, ranging from less than 0.01 microgram/ml to greater than 500 micrograms/ml.

Strategies for production of monoclonal anti-idiotype antibodies against human B cell lymphomas

Murine monoclonal antibodies (MAB) against the idiotype (Id) of B lymphocyte malignancies are powerful reagents for the study of these diseases, and are potentially useful for treatment. Different strategies for the production of these anti-Id MAB have been compared. Initially, the Id Ig from nonsecreting B cell tumors was "rescued" by human X mouse or human X human hybridization. These somatic cell hybridizations resulted in the secretion of human Ig in 10 and 100% of the fusions, respectively. In a second step, anti-Id MAB were produced by using the "rescued" Id Ig as immunogen. A more streamlined approach is based on a one-step procedure in which the tumor cell suspension is used as immunogen. This method of immunization, coupled with a four-layer ELISA, results in the detection of anti-Id MAB in a frequency of approximately 1% of the total hybrids. By using a pool of 10 different anti-Id MAB, each reactive with the tumor of one patient, we searched for idiotypic relatedness among a panel of 50 additional tumors. No cross-reactions were found, indicating that our current strategy results in the identification of unique idiotypic determinants among human B cell tumors. Idiotypic Ig can be found in the serum of patients with B cell tumors. Among groups of patients, there is a wide spectrum of serum Id levels, ranging from less than 0.01 microgram/ml to greater than 500 micrograms/ml.

In vivo effects of murine hybridoma monoclonal antibody in a patient with T-cell leukemia

A murine monoclonal antibody directed against a normal T-cell differentiation antigen was given to a patient with adult T-cell leukemia. Immunofluorescence staining showed increased amounts of this antigen on the patient's leukemia cells. Using a competition radioimmunoassay, free antigen was not detectable in the serum prior to therapy. Two courses of in vivo therapy were given using a 1-mg dose. Each produced a prompt and dramatic fall in WBC with return to pretreatment levels over the ensuing 24 hr, a pattern similar to that seen with leukopheresis. After the first dose of antibody, circulating free antigen became detectable in the serum and a transient decline in creatinine clearance was noted. A 5-mg dose of antibody given at that time was ineffective, presumably because it was blocked by free antigen. Antigenic modulation by leukemia cells was found transiently following each course of antibody. A weak and clinically insignificant host antimouse antibody response was found 5 days after the first treatment. The patient tolerated antibody therapy without difficulty. Monoclonal antibodies offer promise as an immunotherapeutic approach to cancer but problems encountered here must be addressed.

The use of a monoclonal anti-idiotype antibody to study the biology of a human B cell lymphoma

Immunoglobulin was obtained from the tumor cells of a patient with nodular lymphoma by hybridization to mouse myeloma cells. The human immunoglobulin secreted by these hybridoma cells was used as an immunogen to make murine monoclonal antibodies. Antibodies specific for idiotype, mu heavy chain and lambda light chain, were produced. One anti-idiotype antibody was used to document that idiotype-positive cells and low levels of 19S IgM idiotype were present in the patient's blood. The levels of each were found to correlate with the patient's disease activity. The monoclonal anti-idiotype was effective in eliminating idiotype-positive cells in vitro by solid phase absorption or by complement-mediated cytotoxicity. The anti-idiotype was also used to analyze the host's immunologic response to his own tumor idiotype. There was neither a detectable anti-idiotype antibody response produced in vivo nor a detectable population of T cells that expressed idiotype of could bind idiotype.

The use of a monoclonal anti-idiotype antibody to study the biology of a human B cell lymphoma

Immunoglobulin was obtained from the tumor cells of a patient with nodular lymphoma by hybridization to mouse myeloma cells. The human immunoglobulin secreted by these hybridoma cells was used as an immunogen to make murine monoclonal antibodies. Antibodies specific for idiotype, mu heavy chain and lambda light chain, were produced. One anti-idiotype antibody was used to document that idiotype-positive cells and low levels of 19S IgM idiotype were present in the patient's blood. The levels of each were found to correlate with the patient's disease activity. The monoclonal anti-idiotype was effective in eliminating idiotype-positive cells in vitro by solid phase absorption or by complement-mediated cytotoxicity. The anti-idiotype was also used to analyze the host's immunologic response to his own tumor idiotype. There was neither a detectable anti-idiotype antibody response produced in vivo nor a detectable population of T cells that expressed idiotype of could bind idiotype.

Bile secretory apparatus: evidence for a vesicular transport mechanism for proteins in the rat, using horseradish peroxidase and [125I]insulin

The morphologic mechanisms involved in the uptake, transport, and secretion of proteins into bile were studied in rat liver in vivo. When both horseradish peroxidase (HRP) and insulin were injected into the portal veins of anesthetized rats, these proteins were subsequently detected in bile. Utilizing the technique of combined cytochemistry and quantitative autoradiography, both HRP and [125I]insulin were coincidentally localized within endocytic vesicles within the interior of hepatocytes at various time points after simultaneous intraportal injection. The data suggest that both proteins followed two pathways involving endocytic vesicles of approximately 1000 A in diameter. In the first pathway these protein-containing vesicles were transported through the hepatocyte and subsequently fused with the bile canalicular membrane, resulting in secretion of contained proteins into the biliary space. The second pathway also involved endocytosis into 1000 A vesicles, but these vesicles were transported to the Golgi region and its associated system of lysosomes and endoplasmic reticulum (GERL). Whether the proteins in these vesicles were later secreted into bile was unclear. Measurement of HRP and [125I]insulin or its metabolites, in bile, provided direct evidence that exogenously administered proteins (or their fragments) gain entrance into the biliary space. Studies in which metabolites of [125I]insulin, [125I]monoiodotyrosine (MIT), and 125I, were injected intraportally, demonstrated that less than 10% of [125I]MIT and less than 1.5% of Na125I were retained in perfusion-fixed and processed liver tissue. This study suggests that proteins in blood plasma are taken up by hepatocytes and secreted into bile via a vesicular transport mechanism.