Interleukin 2 gene therapy of colorectal carcinoma with autologous irradiated tumor cells and genetically engineered fibroblasts: a Phase I study.

The purpose of this study was to determine the safety, toxicity, and antitumor immune response following S.C. immunizations with a mixture of irradiated, autologous tumor cells and autologous fibroblasts that were genetically modified to express the gene for interleukin 2 (IL-2) in patients with colorectal carcinoma. Ten patients were treated with a fixed dose of tumor cells (10(7)) and escalating doses of fibroblasts secreting IL-2 (per 24 h): 100 units (three patients), 200 units (three patients), 400 units (three patients), and 800 units (one patient). Pre- and posttreatment peripheral blood mononuclear cells were evaluated for evidence of antitumor immune responses. Fatigue and/or flu-like symptoms were experienced by seven patients and delayed-type hypersensitivity-like skin reactions were observed at the sites of the second or subsequent vaccinations in five patients. Low frequencies of tumor cytotoxic T-cell precursors (range, 1/190,000-1/1,320,000 peripheral blood mononuclear cells) were detected prior to therapy in four of seven patients. There was a 5-fold increase following treatment in the frequency of tumor cytotoxic T-cell precursors in two of six evaluable patients. Some patients with colorectal cancer have low frequencies of tumor cytotoxic T-cell precursors that may be increased by this well-tolerated form of IL-2 gene therapy, which warrants continued clinical evaluation.

Combination of transforming growth factor beta antisense and interleukin-2 gene therapy in the murine ovarian teratoma model.

The immunosuppressive protein transforming growth factor beta (TGF-beta) inhibits the activation of various immune effector cells including cytotoxic T lymphocytes and may therefore inhibit the efficacy of immunostimulatory interleukin-2 (IL-2) gene therapy. In this study, we investigated the effect of TGF-beta downregulation on IL-2 gene therapy in the intraperitoneal model of murine ovarian teratoma (MOT). MOT cells, like many human ovarian carcinomas, were found to produce TGF-beta. Production of TGF-beta by MOT cells was suppressed using a TGF-beta antisense plasmid vector (pCEP4/TGF-beta antisense). Subcutaneous immunization of C3H mice with a mixture of IL-2 gene-transduced fibroblasts and TGF-beta antisense-modified MOT cells induced significantly better protection against a subsequent intraperitoneal tumor challenge compared with immunization with unmodified MOT cells alone [11/16 (69%) vs 4/21 (19%) tumor-free animals, P < 0.01]. Immunization with either a mixture of IL-2 gene modified fibroblasts and unmodified MOT cells [2/12 (17%) tumor-free animals] or TGF-beta antisense-modified MOT cells alone (0/13 tumor free animals) failed to induce significant protection compared with immunization with unmodified MOT cells. These data show that combined TGF-beta antisense and IL-2 gene therapy is required to generate effective antitumor responses in the MOT model. Our findings suggest that tumor cell expression of immunosuppressive factors may inhibit cytokine immunogene therapy and may have potential implications for the development of future clinical immunogene therapy protocols.

Antigen-specific IgG responses from naive human splenocytes: in vitro priming followed by antigen boost in the SCID mouse.

High titers of Ag-specific human IgG were consistently achieved in SCID mice reconstituted with human splenocytes that had been primed with Ag in vitro and then boosted with Ag after engraftment into SCID mice. Specific human IgG titers in the hu-SPL-SCID mice reached approximately 1:4 x 10(5) when the mice were immunized with a neo-antigen, whereas titers reached 1:2 x 10(6) when recall responses were induced. Booster immunizations with Ag 21 days after the initial in vivo boost further enhanced this response, and specific human IgG titers of 1:17 x 10(6) were achieved. This represented an essentially monospecific IgG population. These responses were CD4+ T cell dependent. In addition, affinity maturation of the human Ab responses was observed. Spleens of hu-SPL-SCID mice with Ag-specific titers < or = 1:1 x 10(6) were often significantly enlarged and often displayed visible tumors. Fourteen of sixteen B cell tumors removed from spleens of five such hu-SPL-SCID mice, produced Abs that were specific for the immunizing Ags. From such tumor, cloned cell lines were established. One such mAb, MLN-7 (gamma1, kappa), was raised to tetanus toxoid and had no identified cross-reactivity.

IDEC-C2B8: results of a phase I multiple-dose trial in patients with relapsed non-Hodgkin's lymphoma.

PURPOSE: To evaluate the safety, pharmacokinetics, and biologic effect of multiple doses of the chimeric anti-CD20 monoclonal antibody (mAb) IDEC-C2B8 in patients with relapsed B-cell lymphoma. PATIENTS AND METHODS: Twenty patients with relapsed low-grade (n = 15) or intermediate-/high-grade (n = 5) lymphoma received weekly infusions times four of 125 mg/m2 (n = 3), 250 mg/m2 (n = 7), or 375 mg/m2 (n = 10) of IDEC-C2B8. RESULTS: Infusional side effects during the initial infusion were mainly grade I/II fever, asthenia, chills, nausea, rash, and urticaria. More serious events were rare. Peripheral-blood B cells were rapidly depleted and slowly recovered over 3 to 6 months. There was no change in mean immunoglobulin (Ig) levels. Antibody serum half-life (and maximum concentration [Cmax]) generally increased between the first and fourth infusions (33.2 hours v 76.6 hours, respectively) following the 375-mg/m2 doses. Six of 18 assessable patients had a partial remission (PR), with a median time to disease progression of 6.4 months (range, 3 to 21.7). Minor responses (MRs) were observed in five patients and progressive disease (PD) in seven. Tumor responses occurred in peripheral blood, bone marrow (BM), spleen, bulky lymph nodes, and extranodal sites, and in patients who had relapsed following high-dose myeloablative chemotherapy. Six of 14 patients (40%) with a low-grade histology responded. Four of six with bulky disease had a PR. CONCLUSION: IDEC-C2B8 chimeric anti-CD20 mAb therapy is well tolerated and has clinical activity in patients with relapsed B-cell lymphoma. The 375-mg/m2 dose has been selected for a phase II trial in patients with relapsed low-grade or follicular B-cell lymphoma.

IDEC-C2B8 (Rituximab) anti-CD20 monoclonal antibody therapy in patients with relapsed low-grade non-Hodgkin's lymphoma.

IDEC-C2B8 is a chimeric monoclonal antibody (MoAb) directed against the B-cell-specific antigen CD20 expressed on non-Hodgkin's lymphomas (NHL). The MoAb mediates complement and antibody-dependent cell-mediated cytotoxicity and has direct antiproliferative effects against malignant B-cell lines in vitro. Phase I trials of single doses up to 500 mg/m2 and 4 weekly doses of 375 mg/m2 showed clinical responses with no dose-limiting toxicity. We conducted a phase II, multicenter study evaluating four weekly infusions of 375 mg/m2 IDEC-C2B8 in patients with relapsed low-grade or follicular NHL (Working Formulation groups A-D). Patients were monitored for adverse events, antibody pharmacokinetics, and clinical response. Thirty-seven patients with a median age of 58 years (range, 29 to 81 years) were treated. All patients had relapsed after chemotherapy (median of 2 prior regimens) and 54% had failed aggressive chemotherapy. Infusional side effects (grade 1-2) consisting of mild fever, chills, respiratory symptoms, and occasionally hypotension were observed mostly with the initial antibody infusion and were rare with subsequent doses. Peripheral blood B-cell depletion occurred rapidly, with recovery beginning 6 months posttreatment. There were no significant changes in mean IgG levels and infections were not increased over what would be expected in this population. Clinical remissions were observed in 17 patients (3 complete remissions and 14 partial remissions), yielding an intent to treat response rate of 46%. The onset of these tumor responses was as soon as 1 month posttreatment and reached a maximum by 4 months posttreatment. In the 17 responders, the median time to progression was 10.2 months (5 patients exceeding 20 months). Likelihood of tumor response was associated with a follicular histology, with the ability to sustain a high serum level of antibody after the first infusion, and with a longer duration of remission to prior chemotherapy. One patient developed a detectable but not quantifiable immune response to the antibody that had no clinical significance. IDEC-C2B8 in a dose of 375 mg/m2 weekly for 4 weeks has antitumor activity in patients with relapsed low-grade or follicular NHL. Results with this brief, outpatient treatment compare favorably with results with standard chemotherapy, and IDEC-C2B8 has a better safety profile. Further studies evaluating IDEC-C2B8 in other types of lymphoma either alone or combined with chemotherapy are warranted.

Radioimmunotherapy of relapsed B-cell lymphoma with yttrium 90 anti-idiotype monoclonal antibodies.

Tumor-specific anti-idiotype (anti-Id) monoclonal antibodies (MoAbs) to B-cell lymphomas have been administered to patients, resulting in significant clinical responses. However, clinical responses have been limited by the emergence of Id-negative lymphoma. To overcome the problem of tumor heterogeneity, we conducted a pilot evaluation of the safety and effectiveness of yttrium 90 (90Y)-labeled anti-Id and shared Id (sId) MoAbs in non-Hodgkin's B-cell lymphoma. Nine patients with relapsed B-cell lymphoma in whom tumor was successfully targeted with 111In-labeled anti-Id MoAb were treated with 90Y-labeled anti-Id MoAb. A total of 19 courses (one to four per patient) were administered using 1,000 to 2,320 mg unlabeled clearing MoAb and 10 to 54 mCi 90Y MoAb per patient. Two of nine patients had a complete response, one a partial response, three stable disease, and three disease progression. Time to progression varied from 1 to 12 months. Toxicities were predominately hematologic, and only one patient developed infection and required transfusion. At progression, three of five assessable patients had Id-positive lymphoma and two had Id-negative lymphoma. Human antimouse antibodies (HAMA) did not develop in the patients after treatment. 90Y anti-Id MoAbs demonstrated excellent in vivo stability, produced significantly tumor regression in three of nine patients, exhibited acceptable toxicities, and elicited no HAMA formation. Further investigation of repetitive, low-dose 90Y anti-Id and MoAb therapy is warranted; however, the advantages of a pan B MoAb may prove the latter to be the agent of choice for the radio immunotherapy of B-cell lymphoma.

Eradication of established intracranial rat gliomas by transforming growth factor beta antisense gene therapy.

Like human gliomas, the rat 9L gliosarcoma secretes the immunosuppressive transforming growth factor beta (TGF-beta). Using the 9L model, we tested our hypothesis that genetic modification of glioma cells to block TGF-beta expression may enhance their immunogenicity and make them more suitable for active tumor immunotherapy. Subcutaneous immunizations of tumor-bearing animals with 9L cells genetically modified to inhibit TGF-beta expression with an antisense plasmid vector resulted in a significantly higher number of animals surviving for 12 weeks (11/11, 100%) compared to immunizations with control vector-modified 9L cells (2/15, 13%) or 9L cells transduced with an interleukin 2 retroviral vector (3/10, 30%) (P < 0.001 for both comparisons). Histologic evaluation of implantation sites 12 weeks after treatment revealed no evidence of residual tumor. In vitro tumor cytotoxicity assays with lymph node effector cells revealed a 3- to 4-fold increase in lytic activity for the animals immunized with TGF-beta antisense-modified tumor cells compared to immunizations with control vector or interleukin 2 gene-modified tumor cells. These results indicate that inhibition of TGF-beta expression significantly enhances tumor-cell immunogenicity and supports future clinical evaluation of TGF-beta antisense gene therapy for TGF-beta-expressing tumors.

Comparison of gene therapy with interleukin-2 gene modified fibroblasts and tumor cells in the murine CT-26 model of colorectal carcinoma.

We compared the efficacy of gene therapy mediated by interleukin-2 (IL-2) gene-modified tumor cells to gene therapy mediated by IL-2 transduced fibroblasts in the CT-26 model of murine colorectal carcinoma. We transduced CT-26 tumor cells and BALB/c 3T3 fibroblasts with three different retroviral vectors using three different promoters for the human IL-2 gene: DC/TKIL-2 (thymidine kinase promoter), LXSN-iIL2 (long terminal repeat promoter), and LNCX-iIL2 (cytomegalovirus promoter). These transductions resulted in CT-26 and 3T3 subclones that secreted different amounts of IL-2. Immunization of animals with either CT-26/IL-2 cells or with fibroblast/IL-2 cells mixed with CT-26 induced similar levels of immunity that protected 62-82% of animals against a subsequent tumor challenge with parental CT-26. However, mice developed tumors at the site of inoculation in 46% of the animals immunized with CT-26/IL-2 cells. In a separate experiment, CT-26/IL-2 cells were exposed to 6,000 cGy of gamma irradiation to prevent tumor growth at the site of inoculation. Although the CT-26/IL-2 cells continued to secrete IL-2 after irradiation, they were no longer effective at inducing antitumor immunity. In contrast, both irradiated and nonirradiated fibroblast/IL-2 cells, mixed with irradiated CT-26, were equally effective at inducing antitumor immunity. These data suggest that in the CT-26 model, fibroblast-mediated IL-2 gene therapy has advantages for the induction of antitumor immunity and abrogation of tumorigenic potential at the site of inoculation compared with tumor cell-mediated IL-2 gene therapy.

Cytokine gene therapy with interleukin-2-transduced fibroblasts: effects of IL-2 dose on anti-tumor immunity.

We evaluated the effects of different doses of interleukin-2 (IL-2)-transduced fibroblasts in the treatment of colorectal carcinoma in the CT-26 murine tumor model. Immunization with a mixture of irradiated tumor cells and IL-2-transduced fibroblasts (100 units of IL-2/24 hr) induced significantly greater protection against a live tumor challenge compared to irradiated tumor cells alone (22/35, 65% vs. 10/30, 33%, p < 0.02). Protective effects were observed with doses of IL-2-transduced fibroblasts secreting from 5 to 100 units of IL-2/24 hr. Parallel experiments in nude mice produced no protection, indicating that the effects of immunization were mediated by a T-cell-dependent mechanism. In animals with established tumors, complete tumor remissions were observed following immunization with a mixture of irradiated tumor cells and IL-2-transduced fibroblasts secreting 100 units of IL-2/24 hr, but not after immunization with irradiated tumor cells alone (7/16 vs. 0/11 complete remissions, p < 0.02). Fibroblasts secreting higher doses of IL-2 were ineffective in generating systemic immunity, but were required to prevent tumor implantation. A statistically significant difference in the prevention of tumor implantation was observed between groups inoculated with a mixture of live tumor cells and IL-2-transduced fibroblasts (1,750 units of IL-2/24 hr) compared to control fibroblasts (6/8 vs. 0/12, p < 0.001). Similar results were observed in nude mice, suggesting that the implantation rejection response is mediated in part by cells other than thymus-derived T cells. Our data support the utility of IL-2-transduced fibroblasts and indicate that the level of IL-2 expression is an important variable in activating different effector components of antitumor immune responses in IL-2 gene therapy.

Interleukin-2 gene therapy in a patient with glioblastoma.

A patient with glioblastoma multiforme (GBM) who had failed conventional therapy was treated with IL-2 gene therapy. The patient received 10 subcutaneous immunizations with autologous tumor cells and fibroblasts genetically modified to secrete IL-2 by retroviral gene transfer. An antitumor immune response mediated in part by CD8+ cytotoxic T cells was demonstrated with the patient's peripheral blood mononuclear cells. A magnetic resonance imaging (MRI) scan performed 4 weeks after the highest treatment dose revealed marked tumor necrosis. These results support the evaluation of this form of IL-2 gene therapy in additional patients with glioblastoma.

Phenotypic markers and BCL-1 gene rearrangements in B-cell chronic lymphocytic leukemia: a Cancer and Leukemia Group B study.

The markers, CD11b, CD11c, CD14, CD21, CD23, CD25, CD38, and FMC7 were correlated with morphologic and other laboratory and clinical characteristics of 127 patients with untreated CD5+ chronic lymphocytic leukemia (CLL). Only CD38 and CD21 were significantly associated with atypical CLL morphology. The integrin associated markers CD11b and CD11c were associated with lower leukocyte count (white blood cell count [WBC]) and lower Rai stage. By contrast, the activation antigen CD23 was associated with a higher WBC, higher Rai stage, younger age group, and the presence of lymphadenopathy. Therefore, we conclude that CD23 positivity may reflect a more aggressive form of CLL, and CD11b and CD11c positivity a less aggressive form. The BCL-1 gene rearrangement was present in 5 of 84 (6%) CLL cases examined and was associated with atypical morphology and surface expression of CD11b. Patients with a BCL-1 gene rearrangement may represent a CLL subset or possibly a different B-cell disease.

Factors affecting production of antibodies to prostate antigens by in vitro-primed human splenocytes.

Efficiency of immunization of splenocytes in vitro by three kinds of prostate antigen has been studied. Intact cells of the human prostate cell line LNCaP, a membrane preparation (PMA) of LNCaP cells, and prostate specific antigen (PSA) were used as antigens. Three different schemes of in vitro immunization were tested: male spleen cells vs female; single donor spleen cells vs. mixed lymphocyte culture (MLC); addition of exogenous IL-2 vs. no lymphokine addition. The supernatant antibodies were tested for reactivity to the immunizing antigen by ELISA. Subsequently hybridomas were generated by fusing the primed lymphocytes to a heteromyeloma cell line, K6H6/B5. Only antigen specific IgM responses could be detected. Intact LNCaP cells induced the highest responses from mixed lymphocyte cultures. PMA also induced the highest responses from mixed lymphocyte cultures of male origin, whereas both single donor and mixed donor spleen cell cultures of female origin responded to PMA. However, anti-PMA responses by mixed lymphocyte cultures of female cells were significantly augmented by addition of IL-2. PSA only induced specific responses from mixed female splenocyte cultures supported with IL-2. Several anti-PMA and -PSA antibodies were generated after somatic fusion of the in vitro primed cells. Two monoclonal IgG antibodies from LNCaP primed spleen cells could be competitively inhibited with tumor membrane antigen.

In vitro priming of human lymphocytes. I. IL-2 and IL-4 requirements.

Induction of antigen-dependent IgM and IgG responses by human in vitro spleen cell cultures were supported by addition of defined lymphokines. Whereas exposure to IL-2 alone throughout both immunization and cultivation period supported the highest antigen-directed responses, antibodies of higher relative affinity to the immunizing antigen were secreted under conditions of shorter IL-2 exposure. Continuous presence of IL-2 supported the antigen-driven responses for up to 15 days, the later part of which was characterized by a very low relative affinity index value. IL-2 supported cultures produced up to 55 times and 36 times more IgM and IgG, respectively, than cultures without added IL-2. Addition of IL-2-neutralizing antibodies throughout the cultivation period abrogated all responses. Addition of IL-4 alone had negligible effect on the antigen-directed IgM responses but supported antigen-independent IgG responses. Neutralization of IL-4 alone had negligible effect on the IgM and IgG responses, whereas neutralization of IL-4 during IL-2 support, resulted in reduction of antigen dependency of responses. Delayed IL-4 neutralization (24 hours) restored some of the antigen sensitivity. IL-4 reduced IL-2-induced, antigen-directed immunoglobulin responses but supported increased antigen-induced, antigen-directed responses, resulting in maximal antigen-specific responses. IL-4 reduced the IL-2-induced immunoglobulin production. IL-2 supported cell division, whereas IL-4 supported prolonged survival. Flow cytometry tests showed that IL-2 primarily induced CD8+ cells (T suppressor/cytotoxic) and OKT-10+ cells (plasma cells) cells, whereas the number of B1+ cells (B cells) decreased. IL-4 induced slight increases in the amount of B1+ cells and CD4+ cells (T helper).

In vitro priming of human lymphocytes. II. Induction of antigen-specific IgG responses by repeated antigen stimulation.

A protocol by which a human spleen cell culture could be subjected to both a primary and a secondary type immunization in vitro has been developed. Primary immunized cultures required the addition of autologous fresh cells at the time of antigen re-exposure for generation of optimal antigen-specific IgG responses. Antigen re-exposure (secondary stimulation) was done 10 days after initial immunization. Subsequent responses were characterized by novel or greatly enhanced antigen-directed IgG responses compared to primary antigen stimulation. Re-exposure of antigen to 10-day old human spleen cell cultures, without addition of fresh cells, did not result in measurable responses. Lethal irradiation of the fresh cell component of a restimulation culture showed that the IgG responses were derived from the original culture and not the fresh cells. The presence of antigen during both the primary and the secondary immunization was a prerequisite for induction of antigen-directed IgG responses, as spleen cell preparations that had been cultivated without antigen, during the primary stimulation period or the secondary stimulation period or both, did not show antigen-dependent IgG responses after the secondary cultivation. Induction of IgG responses by restimulation was supported by IL-2, but only when IL-2 was added to both the primary and the secondary culture according to a strict protocol. IL-4 added during the second antigen exposure supported antigen-directed responses, whereas IL-4 added during the initial antigen exposure abrogated all antigen-dependent responses.

The effects of postinduction intensification treatment with cytarabine and daunorubicin in adult acute lymphocytic leukemia: a prospective randomized clinical trial by Cancer and Leukemia Group B.

Cancer and Leukemia Group B undertook a randomized trial of intensification treatment in adults aged 15 to 79 years with acute lymphocytic leukemia (ALL) in complete remission (CR). Daunorubicin (DNR), prednisone, vincristine (VCR), intrathecal (IT) methotrexate (MTX), and asparaginase produced 177 CRs in 277 patients. One hundred fifty-one patients were randomly assigned to receive treatment as follows: 74 received intensive cytarabine and DNR, and 77 received cycles of mercaptopurine (6-MP) and MTX, followed by 6MP, MTX, VCR, and prednisone for 3 years in all. One hundred twelve patients received CNS prophylaxis. Intensification produced major myelosuppression but did not improve remission duration (median, 21 months). Of the 151 patients with CRs who entered the intensification phase, 29% remain in continuous CR (43 to 117 months); in 19 patients, CRs have lasted for longer than 7 years. No relapses occurred after 60 months. Median survival from the time of randomization was 30 months. Those under 30 years of age responded more frequently, with longer CR and survival. While 53% of those aged 15 to 19 years remain in continuous CR, 92% of patients over 59 years have relapsed. The presence of a myeloid antigen on the leukemic cells was adversely prognostic for CR achievement and for survival. Pretreatment WBC and platelet levels independently affected CR duration and survival. Early M1 marrow development presaged longer remissions. CNS relapse occurred in 47 of 256 patients with normal CSF before treatment, in 29 before CNS prophylaxis. CNS disease occurred after CNS prophylaxis in 18 patients: 13 of 61 who had received standard premaintenance and five of 51 who received intensification. No advantage in CR duration or survival resulted from intensive treatment with DNR and cytarabine following induction of CR.

Production of antigen-specific human monoclonal antibodies from in vitro-primed human splenocytes.

We have developed culture conditions for human lymphocytes that support primary in vitro immune responses to protein Ag of either human or nonhuman origin. We now show that these primed B cells can be efficiently immortalized by fusion with a heterohybrid fusion partner to generate human, Ag-specific IgM or IgG antibody-producing heterohybridomas at a rate of 17 to 50 hybrids/10(6) lymphocytes fused. Approximately 50% of the Ig-secreting clones were stable with respect to Ig secretion. Levels of secretion attained with terminal cultures ranged from less than 1 to 100 micrograms/ml. Fusions of cells between 2 and 5 days after initiation of in vitro exposure to Ag produced more Ag-reactive and Ag-specific antibodies than fusions at 1 day or fusions performed after 5 days. Ag-reactive hybrids could be isolated at frequencies of 3 to 10%, depending on antigenicity of the immunogen. Foreign proteins, horse spleen ferritin, and a murine monoclonal Ig, induced higher percentages of Ag-reactive mAb than immunization with the human-derived ferritin. Ag-reactive IgG mAb were produced at relatively high frequency, depending on immunization conditions and the nature of the Ag. The strategy for identification of the best hybrids included early elimination of unstable hybridomas and of hybridomas producing broadly cross-reactive antibody, followed by evaluation of units of Ag reactivity/micrograms Ig. Ferritin-specific mAb selected according to these criteria showed immunocytochemical reactivity with ferritin-containing tissues and apparent affinities in the range of 10(7) to 10(8)/mol.

Expression of shared idiotypes in chronic lymphocytic leukemia and small lymphocytic lymphoma.

The expression of shared idiotypes (Slds) has been studied on malignant CD5+B cells from patients with chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) using a panel of 37 murine monoclonal antibodies previously demonstrated to be reactive with Slds derived from follicular B-cell lymphomas. Thirteen anti-Slds identified tumor cells from 31 of 105 (30%) CLL patients and 4 of 6 SLL patients. In comparison, the same panel of anti-Slds is reactive with 33% of follicular and diffuse B-cell lymphomas. Ten of these anti-Slds reacted with CLL cases at similar frequencies to that of the B-cell lymphomas. Two anti-Slds, which are known to react with autoantibodies, were significantly more prevalent in CLL than in B-cell lymphomas. These data confirm the presence of Slds in CLL and provide further evidence of an association between CLL and autoimmunity. The identification of a panel of antibodies reactive with a significant number of CLL and SLL patients will facilitate the application of anti-idiotype antibody therapy in these diseases.