Costimulation of human natural killer cell proliferation: role of accessory cytokines and cell contact-dependent signals

Despite the importance of natural killer (NK) cells in the immune response, the regulation of human NK cell growth has not been well characterized. We have hypothesized that, similar to the proliferation of T and B lymphocytes, optimal proliferation of NK cells requires costimulatory signals as well as a primary mitogenic stimulus. Evidence for costimulation by both soluble cytokines and cell contact-dependent factors is presented. Soluble IL-1 and TNF were found to augment NK cell proliferation in response to primary mitogenic cytokines, including IL-2, IL-4, IL-7, and IL-12. The costimulatory effect of IL-1 and TNF is strongly enhanced by the calcium ionophore ionomycin. Coculture of NK cells with irradiated K562 cells can largely substitute for the costimulatory signal provided by ionomycin. Costimulation by K562 requires intimate cell contact and is not reconstituted by cell-free supernatants. Activated T lymphocytes can also mediate contact-dependent costimulation of NK cells; resting PBMC, several NK-sensitive cell lines, and all NK-resistant cell lines tested were not found to be costimulatory. Engagement of CD16 did not augment NK cell proliferation. Thus, triggering of natural killing or antibody-dependent cell-mediated cytotoxicity (ADCC) does not consistently provide a costimulatory signal for NK cell proliferation. Cell contact-dependent costimulation of NK cells does not appear to involve known receptors that can costimulate T cells, including CD2, CD27, CD28, CD29, or LFA-1. The molecular nature of the putative NK cell costimulatory receptor remains to be elucidated. Nevertheless, human NK cells could be expanded in vitro using leukocyte-conditioned medium (LCM) as a source of IL-2 and accessory cytokines and ionomycin to bypass the putative receptor for cell contact-dependent costimulation. NK cells expanded in LCM and ionomycin express typical NK cell antigens and mediate natural killing and ADCC. Further characterization of the costimulatory signals for NK cell proliferation may elucidate the physiologic regulation of NK cell growth and may ultimately allow more effective manipulation of these lymphocytes in the immunotherapy of human diseases.

Altered tyrosine phosphorylation via the very late antigen (VLA)/beta1 integrin stimulation is associated with impaired T-cell signaling through VLA-4 after allogeneic bone marrow transplantation

Our previous study showed that the cross-linking of very late antigen (VLA)/beta1 with anti-CD29 monoclonal antibody (MoAb), or interactions with extracellular matrix (ECM) proteins through VLA/beta1, failed to induce T-cell costimulation via the CD3/T cell receptor (TCR) pathway for over 1 year after allogeneic bone marrow transplantation (allo-BMT), although normal CD29 and CD3 expression was observed after 3 months following allo-BMT. Molecular analysis revealed altered tyrosine phosphorylation of cellular proteins by the solid-phase cross-linking of VLA/beta1 molecules in T cells from patients after allo-BMT. In T cells from early allo-BMT patients (<4 months), various sizes of highly tyrosine phosphorylated proteins were observed as high background even without the stimulation through VLA/beta1 integrin. The high tyrosine phosphorylation pattern gradually disappeared and it was finally returned to normal tyrosine phosphorylation patterns by 2 years after BMT. Interestingly, poor expression of focal adhesion kinase (pp125FAK), a VLA/beta1-mediated signaling molecule, was observed within 1 year after BMT. These results suggest that these molecular defects appear to be implicated in the impaired VLA/beta1-mediated signaling in T cells from patients after allo-BMT, and it could explain, in part, the persistent immunoincompetent state after allo-BMT at least 1 year.

In vivo adsorption of isohemagglutinins with fresh frozen plasma in major ABO-incompatible bone marrow transplantation

Despite techniques to deplete red cells from major ABO-incompatible allogeneic bone marrow (BM) or to remove recipient isohemagglutinins (IHGs) before transplantation, delayed erythropoiesis and hemolysis, red cell aplasia, and increased red cell transfusion requirements may occur. Twenty-nine recipients of major ABO-incompatible allografts received donor-type frozen fresh plasma (FFP) infusions twice daily to adsorb IHGs in vivo. Engraftment and transfusion requirements were compared between the 29 FFP-treated major ABO-incompatible allograft recipients, 5 recipients of major ABO-incompatible BM who did not receive FFP infusions, 35 recipients of minor ABO-incompatible BM, and 172 recipients of ABO-compatible BM. No significant differences in either transfusion requirements or engraftment were seen in the FFP-treated major ABO-incompatible vs. minor ABO-incompatible or ABO-compatible groups (p values > or = 0.10). The infusion of donor-type FFP represents a simple, effective treatment strategy to neutralize IHGs and to prevent adverse consequences of major ABO incompatibility in the setting of allogeneic BM transplantation. The role of this strategy in the care of patients receiving ABO-incompatible solid organs remains to be defined.

Autologous versus unrelated donor allogeneic marrow transplantation for acute lymphoblastic leukemia

Bone marrow transplantation (BMT) can cure patients with high-risk or recurrent acute lymphoblastic leukemia (ALL). Those lacking a related donor can receive either autologous or histocompatible unrelated donor (URD) marrow. Autotransplantation may result in higher risk of relapse, whereas URD allografts, although associated with serious posttransplant toxicities, may reduce relapse risk. Six years (1987 to 1993) of consecutive autologous BMT (University of Minnesota, Dana Farber Cancer Institute; n = 214) were compared with URD transplants (National Marrow Donor Program; n = 337). Most transplants (70% autologous, 48% URD) were in early remission (first or second complete remission [CR1 or CR2]); 376 patients (75% autologous, 64% URD) were less than 18 years old. Autologous BMT led to significantly lower transplant-related mortality (TRM; relative risk [RR] 0.35; P = .001). URD transplantation offered greater protection against relapse (autologous RR 3.1; P = .001). Patients greater than 18 years old, women, and BMT recipients beyond CR2 had higher TRM, whereas adults, BMT recipients in CR2+, or BMT recipients during 1991 through 1993 had significantly more relapse. After 25 months median follow-up, 100 URD and 56 autologous recipients survive leukemia free. URD BMT in CR2 resulted in superior disease-free survival (DFS), especially for adult patients. Multivariate analysis showed superior DFS for children, men, and BMT during CR1 or 2. Autologous and URD BMT can extend survival for a minority of patients unlikely to be cured by chemotherapy, and the results with either technique are comparable. Greater toxicity and TRM after URD BMT are counterbalanced by better protection against relapse. Prospective studies addressing additional clinical variables are needed to guide clinical decision making about transplant choices for patients with ALL.

Tumor-induced suppression of T lymphocyte proliferation coincides with inhibition of Jak3 expression and IL-2 receptor signaling: role of soluble products from human renal cell carcinomas

The proliferative capacity of T cells infiltrating human tumors is known to be impaired, possibly through their interaction with tumor. Here we demonstrate that soluble products derived from renal cell carcinoma (RCC-S) explants but not normal kidney can inhibit an IL-2-dependent signaling pathway that is critical to T cell proliferation. A major target of the immunosuppression was the IL-2R-associated protein tyrosine kinase, Janus kinase 3 (Jak3). RCC-S suppressed basal expression of Jak3 and its increase following stimulation with anti-CD3/IL-2. Jak3 was most sensitive to suppression by RCC-S; however, reduction in expression of p56(lck), p59(fyn), and ZAP-70 was observed in some experiments. Expression of other signaling elements linked to the IL-2R (Jak1) and the TCR (TCR-zeta, CD3-epsilon, and phospholipase C-gamma) were minimally affected. In naive T cells, RCC-S also partially blocked induction of IL-2R alpha-, beta- and gamma-chain expression when stimulating via the TCR/CD3 complex with anti-CD3 Ab. To determine whether RCC-S suppressed IL-2-dependent signaling, primed T cells were employed since RCC-S had no effect on IL-2R expression but did down-regulate Jak3 expression and, to a lesser degree, p56(lck) and p59(fyn). Reduction in Jak3 correlated with impaired IL-2-dependent proliferation and signal transduction. This included loss of Jak1 kinase tyrosine phosphorylation and no induction of the proto-oncogene, c-Myc. These findings suggest that soluble products from tumors may suppress T cell proliferation through a mechanism that involves down-regulation of Jak3 expression and inhibition of IL-2-dependent signaling pathways.

Tumor-induced suppression of T lymphocyte proliferation coincides with inhibition of Jak3 expression and IL-2 receptor signaling: role of soluble products from human renal cell carcinomas

The proliferative capacity of T cells infiltrating human tumors is known to be impaired, possibly through their interaction with tumor. Here we demonstrate that soluble products derived from renal cell carcinoma (RCC-S) explants but not normal kidney can inhibit an IL-2-dependent signaling pathway that is critical to T cell proliferation. A major target of the immunosuppression was the IL-2R-associated protein tyrosine kinase, Janus kinase 3 (Jak3). RCC-S suppressed basal expression of Jak3 and its increase following stimulation with anti-CD3/IL-2. Jak3 was most sensitive to suppression by RCC-S; however, reduction in expression of p56(lck), p59(fyn), and ZAP-70 was observed in some experiments. Expression of other signaling elements linked to the IL-2R (Jak1) and the TCR (TCR-zeta, CD3-epsilon, and phospholipase C-gamma) were minimally affected. In naive T cells, RCC-S also partially blocked induction of IL-2R alpha-, beta- and gamma-chain expression when stimulating via the TCR/CD3 complex with anti-CD3 Ab. To determine whether RCC-S suppressed IL-2-dependent signaling, primed T cells were employed since RCC-S had no effect on IL-2R expression but did down-regulate Jak3 expression and, to a lesser degree, p56(lck) and p59(fyn). Reduction in Jak3 correlated with impaired IL-2-dependent proliferation and signal transduction. This included loss of Jak1 kinase tyrosine phosphorylation and no induction of the proto-oncogene, c-Myc. These findings suggest that soluble products from tumors may suppress T cell proliferation through a mechanism that involves down-regulation of Jak3 expression and inhibition of IL-2-dependent signaling pathways.

CD94 ligation induces apoptosis in a subset of IL-2-stimulated NK cells

CD94 (Kp43) is a member of the human C-type lectin superfamily encoding type II membrane glycoproteins expressed on NK cells and a subset of T cells. Ligation of CD94 has been shown to either potentiate or inhibit NK cell proliferation and cytolytic effector function. Here we show that CD94 ligation triggers apoptosis in IL-2-primed NK cells. Evidence for CD94-induced apoptosis includes: 1) chromatin condensation as measured by increased fluorescence of Hoechst dye, 2) induction of DNA fragmentation, and 3) characteristic morphology by transmission electron microscopy. IL-2 priming (at least 12 h) is required for activation-induced NK cell death triggered by CD94. Activation-induced NK cell death triggered by CD94 ligation is extremely rapid (DNA fragmentation is first observed at 120 min). Unlike activation-induced T cell death, it is not inhibited by neutralizing Abs reactive with TNF-alpha or Fas ligand. Our results suggest that CD94 may play a role in the elimination of activated NK cells during the transition from the innate to the Ag-specific immune response.

CD94 ligation induces apoptosis in a subset of IL-2-stimulated NK cells

CD94 (Kp43) is a member of the human C-type lectin superfamily encoding type II membrane glycoproteins expressed on NK cells and a subset of T cells. Ligation of CD94 has been shown to either potentiate or inhibit NK cell proliferation and cytolytic effector function. Here we show that CD94 ligation triggers apoptosis in IL-2-primed NK cells. Evidence for CD94-induced apoptosis includes: 1) chromatin condensation as measured by increased fluorescence of Hoechst dye, 2) induction of DNA fragmentation, and 3) characteristic morphology by transmission electron microscopy. IL-2 priming (at least 12 h) is required for activation-induced NK cell death triggered by CD94. Activation-induced NK cell death triggered by CD94 ligation is extremely rapid (DNA fragmentation is first observed at 120 min). Unlike activation-induced T cell death, it is not inhibited by neutralizing Abs reactive with TNF-alpha or Fas ligand. Our results suggest that CD94 may play a role in the elimination of activated NK cells during the transition from the innate to the Ag-specific immune response.

Characterization of T cell repertoire in patients with graft-versus-leukemia after donor lymphocyte infusion

The clinical efficacy of donor lymphocyte infusions (DLI) in patients with relapsed chronic myelocytic leukemia after allogeneic bone marrow transplantation has been demonstrated in several recent studies. Although it is presumed that allogeneic T cells mediate this graft-versus-leukemia (GVL) effect, the influence of DLI on the T cell compartment of recipients has not been determined. To characterize the immunologic effects of DLI and to identify T cell changes selectively associated with the GVL response, we analyzed the T cell receptor (TCR) repertoire in four patients with relapsed chronic myelocytic leukemia who achieved a complete remission after infusion of CD4+ lymphocytes from HLA-identical sibling donors. Only one of the four patients developed clinically significant graft-versus-host disease (GVHD) after infusion of donor lymphocytes. TCR repertoire was examined after PCR amplification of 24 Vbeta gene subfamilies in serial samples obtained over a 1-yr period before and after DLI. Results were compared to 10 normal donors. Before DLI, all four patients were found to have abnormal TCR Vbeta repertoire in peripheral T cells, associated with a large number of clonal and oligoclonal patterns. Abnormal TCR patterns persisted for at least 3 mo after DLI, but thereafter gradually began to normalize. By 1 yr after DLI, all patients demonstrated almost complete normalization of Vbeta repertoire with polyclonal representation within almost all Vbeta gene subfamilies. We also examined changes in the TCR Vbeta repertoire associated with the disappearance of Ph+ cells. In each patient, we were able to identify the expansion of at least 1 Vbeta gene subfamily that coincided with the time of the cytogenetic response. In one patient who was studied in greater detail, CDR3 size analysis of serial samples after DLI indicated that these changes were associated with the appearance of clonal T cells. This finding was confirmed through CDR3 sequence analysis and use of CDR3 clone-specific oligonucleotide probes. A putative GVL clone identified by this technique was not detectable in either donor or patient T cells before DLI, but persisted in peripheral T cells for approximately 1 yr. These experiments therefore provide evidence for the clonal expansion of allogeneic T cells that may be selective mediators of antileukemia activity without also mediating graft-versus-host disease.

Role of the CD40 and CD95 (APO-1/Fas) antigens in the apoptosis of human B-cell malignancies

Ligation of CD40 inhibits apoptosis and stimulates proliferation of normal B cells, whereas ligation of CD95 (APO-1/Fas) induces apoptosis of activated lymphocytes. Aberrant signalling through the CD40 and CD95 antigens could thus participate in the pathogenesis of lymphoid malignancies. The expression and function of CD40 and CD95 on neoplastic B cells from patients with acute lymphoblastic leukaemia (ALL), chronic lymphocytic leukaemia (CLL) and non-Hodgkin's lymphoma (NHL) were examined. CD40 was expressed by all 30 B-cell tumours, whereas CD95 was detected on neoplastic B cells in only one of 10 cases of ALL, two of 10 cases of CLL, and three of 10 cases of NHL. Incubation with an agonistic CD95 monoclonal antibody (MoAb) did not augment apoptosis in any of the unstimulated B-cell neoplasms. CD40 triggering did not consistently inhibit spontaneous apoptosis, but ultimately stimulated the growth of neoplastic B cells in most cases. Furthermore, CD40 activation led to up-regulation of the CD95 antigen in all 30 B-cell neoplasms. Ligation of CD95 on CD40-activated tumour cells augmented apoptosis in five of 10 ALL, three of 10 CLL, and nine of 10 NHL cases. The degree of apoptosis induced by CD95 triggering was greater for NHL cells than for ALL cells or CLL cells. Bcl-2 expression by ALL and NHL cells was substantially decreased after in vitro culture, whereas Bcl-2 expression by CLL cells was not significantly changed. However, there was no correlation between the level of Bcl-2 expression and sensitivity to CD95-mediated apoptosis. Thus, factors other than levels of CD95 and Bcl-2 determine susceptibility of malignant B cells to apoptosis after CD95 triggering. CD40-activated lymphoma cells appear to be very sensitive to CD95-mediated apoptosis, suggesting potential strategies for treatment of NHL. Elucidation of the mechanisms underlying resistance of ALL and CLL cells to CD95 triggering may facilitate the development of novel therapeutic approaches to these diseases as well.

CD6-depleted allogeneic bone marrow transplantation for acute leukemia in first complete remission

The appropriate timing of bone marrow transplantation (BMT) for adults with acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) is controversial. Although allogeneic transplantation results in a lower risk of disease recurrence than intensive chemotherapy alone, overall outcome following BMT may not be improved due to the higher incidence of therapy-related fatal complications, frequently as a result of the development of graft-versus-host disease (GVHD). Selective T-cell depletion of donor marrow can reduce the incidence of GVHD and thereby limit transplant-related toxicity. Herein we report the risk of GVHD, incidence of transplant related mortality (TRM), likelihood of disease relapse, and overall survival in adult patients undergoing BMT with CD6 depleted allogeneic marrow for acute leukemia in first remission. Forty-one consecutive allogeneic transplants were performed on patients with acute leukemia and high-risk features (28 AML, 13 ALL) using T12 monoclonal antibody and complement to remove CD6+ T cells from donor marrow. No pre- or posttransplant immune suppressive medications for GVHD prophylaxis were administered. The actuarial estimated risk of grade 2 to 4 acute GVHD was 15% in patients receiving HLA identical grafts. Chronic GVHD developed in five patients. The estimated risk of TRM for patients in first complete remission was 5% at Day +100 and 16% at 2 years. Fatalities attributable to infection with cytomegalovirus or Epstein-Barr virus occurred in only three patients. Estimated probabilities of relapse, overall survival, and event-free survival at 4 years were 25%, 71%, and 63%, respectively. No significant differences in GVHD, TRM, relapse rate, or survival was observed for patients with AML compared with those with ALL. Allogeneic transplantation with CD6 depleted bone marrow is effective in consolidating remissions of high-risk patients with acute leukemia in first remission without excessive toxicity.

Expression of the IL-2 receptor gamma subunit in resting human CD4 T lymphocytes: mRNA is constitutively transcribed and the protein stored as an intracellular component

IL-2 receptor (IL-2R) is composed of three subunits named IL-2R alpha, IL-2R gamma. Here, we study the expression of the IL-2R gamma in highly purified, resting peripheral human CD4 T lymphocytes. We show by FACS analysis that the IL-2R gamma subunit is not detectable at the cell surface of peripheral CD4 T lymphocytes. This result has been verified after acid treatment of the cell surface and analysis with three specific anti-IL-2R gamma mAb. Using RT-PCR and intracellular FACS analysis, we demonstrate that IL-2R gamma is constitutively expressed at the mRNA level and the protein is stored as an intracellular component in resting CD4 T lymphocytes. IL-2R alpha and beta subunits are not detectable by these methods. In addition, we show that CD4 T cell remain insensitive to a variety of cytokines that share IL-2R gamma as a common subunit of their receptors (e.g. IL-2, IL-4, IL-7 and IL-15). The kinetics of cell surface expression of IL-2R gamma have been studied after activation of CD4 T lymphocytes and compared with induction of IL-2R alpha and IL-2R beta. Maximum expression of IL-2R gamma is observed after 2 days of stimulation, and remains constant and comparable to IL-2R beta up to day 5. We conclude from these studies that IL-2R gamma is translocated to the membrane only after T cell activation and induction of the IL-2R alpha and IL-2R beta genes. We hypothesize that in CD4 T cells a large intracellular pool of IL-2R gamma is present but that its cell surface translocation depends on the expression of alpha and/or beta chains specific for IL-2, IL-4, IL-7, IL-9 or IL-15.

CD6+ T cell depleted allogeneic bone marrow transplantation from genotypically HLA nonidentical related donors

The widespread use of allogeneic bone marrow transplantation (BMT) is limited by the availability of suitable donors. Recent attempts to expand the donor pool by employing HLA matched unrelated marrow have been partially successful. However, severe graft-versus-host disease (GVHD) and graft failure remain obstacles and contribute to the substantial morbidity and mortality associated with matched unrelated BMT. The use of genotypically nonidentical related or unrelated donor marrow could have wider application if problems associated with GVHD could be overcome. Based upon the low incidence of GVHD in recipients of HLA-matched related donor marrow depleted of T cells with T12, an anti-CD6 monoclonal antibody, we applied this approach to 27 adult recipients of HLA mismatched related bone marrow. Ten patients received marrow mismatched at 2 HLA loci, 13 received 1 antigen mismatched marrow, and 4 received phenotypically identical marrow from a non-sibling. Immediately prior to admission, patients were treated with total lymphoid irradiation (750-1050 cGy) to suppress host derived. T lymphocytes capable of mediating graft rejection. The ablative regimen consisted of cyclophosphamide (60 mg/kg x 2 days) followed by total body irradiation (1400 cGy in 7 fractions over 4 days). Patients then received marrow depleted of T cells with T12 (CD6) plus complement. No immune suppressive medications were administered to prevent GVHD. Twenty-four of 27 patients displayed stable hematologic engraftment, achieving an absolute neutrophil count of 0.5 x 10(9)/L at a median of 19 days post-BMT. Degree of HLA disparity did not influence engraftment. Among engrafting patients, grades 2-4 acute GVHD occurred in 40% and grade 3-4 GVHD in 8%. Chronic GVHD developed in 5 patients. Patients mismatched at 2 loci were more likely to develop GVHD than those mismatched at 0-1 loci (logrank, p = .04). Disease relapse has occurred in only 3 patients receiving mismatched marrow. Estimated overall survival for mismatched patients is 56% at 2 years and is independent of HLA disparity. Among the patients transplanted for chronic myelogenous in stable phase or acute leukemia in first remission, estimated event free survival is 69% at 2 years compared to 20% for patients with more advanced disease. Our results suggest that transplantation of mismatched related marrow using modalities designed to reduce GVHD without immune suppressive medication (CD6 depletion) is feasible and should prompt wider investigation into the extended families of patients in the search for potential marrow donors. This approach also merits investigation in recipients of matched unrelated marrow as a potential means of reducing transplant-related toxicity.

Phase I evaluation of intravenous recombinant human interleukin 12 in patients with advanced malignancies

A Phase I dose escalation trial of i.v. administered recombinant human interleukin 12 (rhIL-12) was performed to determine its toxicity, maximum tolerated dose (MTD), pharmacokinetics, and biological and potential antineoplastic effects. Cohorts of four to six patients with advanced cancer, Karnofsky performance >/=70%, and normal organ function received escalating doses (3-1000 ng/kg/day) of rhIL-12 (Genetics Institute, Inc.) by bolus i.v. injection once as an inpatient and then, after a 2-week rest period, once daily for five days every 3 weeks as an outpatient. Therapy was withheld for grade 3 toxicity (grade 4 hyperbilirubinemia or neutropenia), and dose escalation was halted if three of six patients experienced a dose-limiting toxicity (DLT). After establishment of the MTD, eight more patients were enrolled to further assess the safety, pharmacokinetics, and immunobiology of this dose. Forty patients were enrolled, including 20 with renal cancer, 12 with melanoma, and 5 with colon cancer; 25 patients had received prior systemic therapy. Common toxicities included fever/chills, fatigue, nausea, vomiting, and headache. Fever was first observed at the 3 ng/kg dose level, typically occurred 8-12 h after rhIL-12 administration, and was incompletely suppressed with nonsteroidal anti-inflammatory drugs. Routine laboratory changes included anemia, neutropenia, lymphopenia, hyperglycemia, thrombocytopenia, and hypoalbuminemia. DLTs included oral stomatitis and liver function test abnormalities, predominantly elevated transaminases, which occurred in three of four patients at the 1000 ng/kg dose level. The 500 ng/kg dose level was determined to be the MTD. This dose, administered by this schedule, was associated with asymptomatic hepatic function test abnormalities in three patients and an onstudy death due to Clostridia perfringens septicemia but was otherwise well tolerated by the 14 patients treated in the dose escalation and safety phases. The T1/2 elimination of rhIL-12 was calculated to be 5.3-9.6 h. Biological effects included dose-dependent increases in circulating IFN-gamma, which exhibited attenuation with subsequent cycles. Serum neopterin rose in a reproducible fashion regardless of dose or cycle. Tumor necrosis factor alpha was not detected by ELISA. One of 40 patients developed a low titer antibody to rhIL-12. Lymphopenia was observed at all dose levels, with recovery occurring within several days of completing treatment without rebound lymphocytosis. There was one partial response (renal cell cancer) and one transient complete response (melanoma), both in previously untreated patients. Four additional patients received all proposed treatment without disease progression. rhIL-12 administered according to this schedule is biologically and clinically active at doses tolerable by most patients in an outpatient setting. Nonetheless, additional Phase I studies examining different schedules and the mechanisms of the specific DLTs are indicated before proceeding to Phase II testing.

Interferon-gamma and interleukin-4 regulate T cell interleukin-12 responsiveness through the differential modulation of high-affinity interleukin-12 receptor expression

Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) are mutually antagonistic cytokines that stimulate CD4+ T cells to develop into either Th1 or Th2 cells. One feature of Th2 differentiation in mice is the loss of IL-12-induced Jak2 and Stat4 activation, which is accompanied by the inability to produce IFN-gamma in response to IL-12. In this report, we show that freshly isolated human T cells activated with phytohemagglutinin (PHA) in the presence of IL-4 exhibit a greatly diminished response to IL-12, whereas the IL-12 response of T cells activated with PHA plus IFN-gamma is enhanced. Radiolabeled IL-12 binding studies demonstrate that the impairment of T cell IL-12 responsiveness by IL-4 is associated with the down-regulation of high-affinity IL-12 receptor expression. In contrast, the enhancement of IL-12 responsiveness by IFN-gamma is associated with the upregulation of high-affinity IL-12 receptor expression. Through the use of a newly synthesized neutralizing antibody to the low-affinity IL-12 receptor beta subunit (IL-12Rbeta), we show that neither IL-4 nor IFN-gamma affect the expression of IL-12Rbeta, which we determine to be one of at least two low-affinity subunits required for high-affinity IL-12 binding. These findings suggest that IL-4 and IFN-gamma exert opposite effects on T cell IL-12 responsiveness by differentially modulating the expression of low-affinity IL-12 receptor subunits that are distinct from IL-12Rbeta and required, together with IL-12Rbeta, for high-affinity IL-12 binding and IL-12 responsiveness. This provides a basis for understanding the interplay between different cytokines at the level of cytokine receptor expression, and offers insight into one of the mechanisms governing Th1 and Th2 development.

Immunotoxin therapy of small-cell lung cancer: a phase I study of N901-blocked ricin

PURPOSE

Immunotoxins could improve outcome in small-cell lung cancer (SCLC) by targeting tumor cells that are resistant to chemotherapy and radiation. N901 is a murine monoclonal antibody that binds to the CD56 (neural cell adhesion molecule [NCAM]) antigen found on cells of neuroendocrine origin, including SCLC. N901-bR is an immunoconjugate of N901 antibody with blocked ricin (bR) as the cytotoxic effector moiety. N901-bR has more than 700-fold greater selectivity in vitro for killing the CD56+ SCLC cell line SW-2 than for an antigen-negative lymphoma cell line. Preclinical studies suggested the potential for clinically significant cardiac and neurologic toxicity. We present a phase I study of N901-bR in relapsed SCLC.

PATIENTS AND METHODS

Twenty-one patients (18 relapsed, three primary refractory) with SCLC were entered onto this study. Successive cohorts of at least three patients were treated at doses from 5 to 40 microg/kg/d for 7 days. The initial three cohorts received the first day's dose (one seventh of planned dose) as a bolus infusion before they began the continuous infusion on the second day to observe acute toxicity and determine bolus pharmacokinetics. Toxicity assessment included nerve-conduction studies (NCS) and radionuclide assessment of left ventricular ejection fraction (LVEF) before and after N901-bR administration to fully assess potential neurologic and cardiac toxicity.

RESULTS

The dose-limiting toxicity (DLT) of N901-bR given by 7-day continuous infusion is capillary leak syndrome, which occurred in two of three patients at the dose of 40 microg/kg (lean body weight [LBW])/d. Detectable serum drug levels equivalent to effective in vitro drug levels were achieved at the 20-, 30-, and 40-microg/kg(LBW)/d dose levels. Specific binding of the immunotoxin to tumor cells in bone marrow, liver, and lung was observed. Cardiac function remained normal in 15 of 16 patients. No patient developed clinically significant neuropathy. However, a trend was noted for amplitude decline in serial NCS of both sensory and motor neurons. One patient with refractory SCLC achieved a partial response.

CONCLUSION

N901-bR is an immunotoxin with potential clinical activity in SCLC. N901-bR is well tolerated when given by 7-day continuous infusion at the dose of 30 microg/kg(LBW)/d. Neurologic and cardiac toxicity were acceptable when given to patients with refractory SCLC. A second study to evaluate this agent after induction chemoradiotherapy in both limited- and extensive-stage disease was started following completion of this study.

Administration of R24 monoclonal antibody and low-dose interleukin 2 for malignant melanoma

R24 is a monoclonal antibody that recognizes the disialoganglioside GD3 expressed on the surface of malignant melanoma cells. Once bound, it can mediate destruction of these cells through both complement-mediated lysis and antibody-dependent cellular cytotoxicity. Agents such as interleukin 2 (IL-2), which can augment effector cell function and promote destruction of antibody-coated tumor cells, might produce improved antitumor responses when combined with R24. In this series, we evaluated the combination of R24 and IL-2 in a Phase 1b study in patients with metastatic melanoma. Twenty-eight patients with metastatic melanoma were entered into the protocol at two institutions. Patients received 8 weeks of IL-2 by continuous i.v. infusion at a dose (4.5 x 10(5) Amgen units/m2/day) designed to selectively expand natural killer (NK) cells. In weeks 5 and 6, patients received R24 for a total of four doses. Twenty-four h after each R24 infusion, patients received a 2-h bolus dose of IL-2 to help promote activity of NK effectors against antibody-coated melanoma targets. Additional IL-2 boluses were administered in weeks 7 and 8. Doses were escalated through two bolus doses of R24 (5 or 15 mg/m2) and two bolus doses of IL-2 (2.5 or 5.0 x 10(5) units/m2). Although one patient experienced severe capillary leak syndrome during IL-2, therapy was otherwise well tolerated. At the higher dose level of R24, two of four patients experienced transient but severe abdominal and chest discomfort, necessitating dose reduction. One patient with ocular melanoma and liver metastases had a partial response. Two additional patients had minor responses. A dramatic increase in NK cell number was noted as a result of treatment, as was augmentation of cytolytic activity against cultured NK-sensitive targets. Antibody-dependent cellular cytotoxicity against cultured melanoma cells in the presence of exogenous R24 or in the presence of serum obtained from patients following R24 infusion also increased during treatment. Our experience indicates that R24 and low-dose IL-2 can be safely combined in patients with metastatic melanoma and that this combination can promote destruction of cultured melanoma cells. The clinical activity of this combination against ocular melanoma may merit further investigation.

TEL/AML-1 dimerizes and is associated with a favorable outcome in childhood acute lymphoblastic leukemia

Polymerase chain reaction-based screening of childhood acute lymphoblastic leukemia (ALL) samples showed that a TEL/AML1 fusion transcript was detected in 27% of all cases, representing the most common known gene rearrangement in childhood cancer. The TEL/AML1 fusion results from a t(12;21)(p13;q22) chromosomal translocation, but was undetectable at the routine cytogenetic level. TEL/AML1-positive patients had exclusively B-lineage ALL, and most patients were between the ages of 2 and 9 years at diagnosis. Only 3/89 (3.4%) adult ALL patients were TEL/AML1-positive. Most importantly, TEL/AML1-positive children had a significantly lower rate of relapse compared with TEL/AML1-negative patients (0/22 v 16/54, P = .004). Co-immunoprecipitation experiments demonstrated that TEL/AML-1 formed homodimers in vitro, and heterodimerized with the normal TEL protein when the two proteins were expressed together. The elucidation of the precise mechanism of transformation by TEL/AML1 and the role of TEL/AML1 testing in the treatment of childhood ALL will require additional studies.

Prevention of transmission of hepatitis C virus in bone marrow transplantation by treating the donor with alpha-interferon

Transmission of hepatitis C virus (HCV) in the setting of allogeneic bone marrow transplantation can occur through an infected marrow donor. Prevention of transmission may reduce the risks of peritransplant complications. We describe a 43-year-old patient with chronic myelogenous leukemia whose HLA-identical donor was found to be HCV antibody positive and HCV RNA positive by polymerase chain reaction (PCR). The patient was HCV antibody negative and HCV RNA negative by PCR of the serum. For 6 months before bone marrow transplantation, the donor was treated with alpha-interferon at a standard dose. After 3 months, HCV RNA was no longer detectable by PCR. Interferon was discontinued 1 week before harvest. Bone marrow cellularity was normal. Engraftment was prompt. The recipient's serum remained negative for HCV RNA at 1, 3, 5, and 10 months after transplantation. Hepatitis C transmission from a viremic donor to an HCV-seronegative recipient may be preventable by treating the donor with alpha-interferon.

CD2-CD58 interaction and the control of T-cell interleukin-12 responsiveness. Adhesion molecules link innate and acquired immunity

Interleukin-12 is an antigen-presenting cell (APC)-derived cytokine that stimulates T helper cell type 1 (Th1) differentiation as well as proliferation, cytolytic activity, and IFN-gamma production among T and natural killer (NK) cells. By immunizing mice with activated T cells and screening for antibodies that could inhibit IL-12-induced proliferation, CD2 was identified as a regulator of T-cell IL-12 responsiveness. Antibodies specific for the adhesion domain of either CD2 or its primary ligand, CD58, inhibited the major functional responses of T cells to IL-12 without affecting the response to IL-2. This inhibition did not involve any alteration in IL-12 binding to T cells. The CD2-CD58 interaction between activated T cells and monocytes was found to be a critical factor in the modulation of T-cell IL-12 responsiveness, and experiments using CD58-transfected Chinese hamster ovary (CHO) cells, and stimulatory pairs of CD2 antibodies confirmed the key role of CD2 ligation in optimizing T-cell IL-12 signaling. These findings illustrate how APCs, through the differential expression of a specific adhesion molecule, can control the T-cell response to a cytokine independent of cytokine receptor expression. This has important implications for an understanding of Th1 development and the conditions required to link innate with acquired immune responses.

High-dose therapy and autologous bone marrow transplantation in patients with follicular lymphoma during first remission

We report the results of a study in previously untreated advanced stage patients with follicular lymphoma (FL) who underwent uniform induction chemotherapy with cyclophosphamide, doxorubicin, vincristine, prednisone (CHOP) followed by myeloablative therapy and anti-B-cell monoclonal antibody purged autologous bone marrow transplantation (ABMT). Eighty-three patients with previously untreated, low-grade FL were enrolled. After CHOP induction, only 36% achieved complete remission (CR) and 77 patients underwent ABMT. Before BM harvest, 70 patients had a known t(14;18), as determined by polymerase chain reaction (PCR), and all remained PCR positive in the BM at harvest. After ABMT, the disease-free survival (DFS) and overall survival are estimated to be 63% and 89% at 3 years, respectively, with a median follow-up of 45 months. Patients whose BM was PCR negative after purging experienced significantly longer freedom from recurrence (FFR) than those whose BM remained PCR positive (P = .0006). Continued PCR negativity in follow-up BM samples was also strongly predictive of continued CR. This study suggests that a subset of patients with advanced FL may experience prolonged clinical and molecular remissions following high-dose ablative therapy, although longer follow-up will be necessary to determine potential impact on overall survival.

Eradication of polymerase chain reaction-detectable chronic lymphocytic leukemia cells is associated with improved outcome after bone marrow transplantation

In chronic lymphocytic leukemia (CLL), clonal rearrangement of the immunoglobulin heavy chain locus (IgH) provides a useful marker for the detection of minimal residual disease (MRD) after treatment. At the time of initial presentation, DNA from patients with CLL was polymerase chain reaction (PCR)-amplified using consensus Variable (VH) and Joining (JH) region primers using complementarity determining region III consensus region primers or a panel of VH family-specific framework region 1 (FR1) primers. The clonal product was directly sequenced and patient-specific probes constructed using N region nucleotide sequences. We amplified and sequenced the CDRIII region and designed patient specific oligonucleotide probes for the detection of MRD in 55 of 66 patients (84%, 90% Confidence Intervals (CI): 74% to 90%) with poor prognosis CLL referred for autologous and allogeneic bone marrow transplantation (BMT). To determine the clinical utility of this technique, PCR amplification was performed on patient samples at the time of and following autologous (21 patients) and allogeneic (10 patients) BMT in whom serial bone marrow samples obtained after BMT were available for analysis. We show that the persistence of MRD after BMT is associated with increased probability of relapse. In all cases that have relapsed to date, the IgH CDRII region was identical at the time of initial presentation and at relapse suggesting that clonal evolution of the IgH locus is unusual in this disease. The finding that a significant number of patients remain disease free and with no evidence of PCR-detectable MRD after BMT suggests that high-dose therapy may contribute to improved outcome in selected patients with CLL.

Defective activation of mitogen-activated protein kinase after allogeneic bone marrow transplantation

Allogeneic bone marrow transplant (BMT) recipients have increased susceptibility to infections for prolonged periods after phenotypic reconstitution of donor cells. This immunodeficiency status is characterized by multiple T-cell functional abnormalities. This study was designed to investigate several signaling pathways involved in T-cell activation during this period of immune deficiency. In initial experiments using equal numbers of CD3+ cells or highly purified T-cell subpopulations obtained from normal controls and BMT recipients, we confirmed that abnormal T-cell proliferation after CD3 cross-linking, phytohemagglutinin stimulation, or phorbol myristate acetate (PMA) stimulation of peripheral blood mononuclear cells from BMT recipients was due to a qualitative T-cell deficiency rather than to low numbers of circulating T cells. We next investigated the ability of the T-cell receptor/CD3 complex to transduce signals via receptor-associated protein tyrosine kinases. In all BMT recipients, CD3 cross-linking induced protein tyrosine phosphorylation of several proteins in a similar fashion to that seen in controls, including phosphorylation of a 21-kD protein that represents the zeta subunit of the receptor itself. Further investigation showed that CD3 cross-linking and PMA stimulation did not increase 42-44-kD mitogen-activated protein kinase (MAPK) activity. The failure of MAPK activation in BMT recipients occurred despite tyrosine phosphorylation of the 42-44-kD proteins, which, in normal controls, parallels enzyme activation. Our results indicate that T-cell immunodeficiency in BMT recipients is associated with a selective failure of MAPK activation, possibly related to abnormal posttranslational positive regulation of this enzyme.

Sources and sequelae of bacterial contamination of hematopoietic stem cell components: implications for the safety of hematotherapy and graft engineering

BACKGROUND

It is important to compare the incidence of bacterial contamination of components collected from the peripheral blood or bone marrow (BM), as well as of components processed with or without cell selection or depletion, and to evaluate the sequelae of such contamination.

STUDY DESIGN AND METHODS

Bacterial contamination rates were compared in 1380 untreated autologous peripheral blood progenitor cells (PBPCs), 291 untreated autologous BM samples, 916 monoclonal antibody (MoAb)-treated autologous and allogeneic BM samples, and in 45 autologous PBPC components from which the CD34+ cells were selected. Bacterial cultures were performed at sequential time points during the processing of MoAb-treated BM.

RESULTS

Bacterial contamination was documented in 44 of 2632 components from 1593 patients (1.67% of components, 2.76% of patients) before cryopreservation. Although only 0.65% of untreated PBPCs were contaminated before cryopreservation, each patient was more likely to have given a contaminated PBPC component than a contaminated BM component (2.41% vs. 0%, p < 0.01). Bacterial contamination of MoAb-treated BM was greater during or after manipulation than it was before (2.33% vs. 0.77%, p < 0.05). At thawing, contamination was documented in 42 (1.97%) of 2136 components cultured. Ten (13.7%) of 73 patients who received hematopoietic progenitor cells that were contaminated before cryopreservation or at thawing developed fever or positive blood cultures within 48 hours of transfusion. Fever was associated with bacteremia in two cases, but no irreversible clinical sequelae were noted.

CONCLUSION

These studies suggest that, despite careful attention to sterile procedures, low-level contamination of hematopoietic stem cell components can be introduced before or during manipulation as well as at thawing, and that standards for monitoring of the procedures for collection, processing, cryopreservation, thawing, and transfusion of hematopoietic progenitor cells are necessary.