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The expression of cytotoxic T-lymphocyte antigen–4 (CTLA-4) molecule in human normal and neoplastic hematopoietic cells, both on the cell membrane and in the intracellular compartment, was evaluated. Flow cytometric analysis carried out with a panel of anti–CTLA-4 human single-chain fragment of variable domain (scFv) antibodies revealed that CTLA-4 was not expressed on the surface, whereas it was highly expressed within the cytoplasm, in freshly isolated peripheral blood mononuclear cells (PBMCs), T cells, B cells, CD34+stem cells, and granulocytes. Various treatments with agents able to specifically activate each cell type induced CTLA-4 expression on the surface of these cells. Similarly, increased CTLA-4 expression was observed in different hematopoietic cell lines although they also expressed surface CTLA-4, at different degrees of intensity, before activation. Surprisingly, CTLA-4 RNA transcripts were detectable in such cell lines only after nested polymerase chain reaction (PCR) specific for CTLA-4 extracellular domain, suggesting a very fast CTLA-4 RNA processing accompanied by prolonged CTLA-4 protein accumulation. We further demonstrated surface expression of CTLA-4 in a variety of acute and chronic myeloid leukemias (AMLs and CMLs) and B- and T-lymphoid leukemias, either adult or pediatric. CTLA-4 was expressed in 25% to 85% of AMLs and CMLs depending on the leukemia subtype and the epitope analyzed, whereas in acute B- and T-leukemias CTLA-4 expression was mainly cytoplasmic. Chronic B leukemias appeared to express CTLA-4, both on the surface and in cytoplasm, whereas few cases tested of chronic T leukemias were negative. Two anti–CTLA-4 immunotoxins (scFvs-saporin) induced in vitro apoptosis of neoplastic cells from a representative AML, suggesting a novel immunotherapeutic approach to AML based on CTLA-4 targeting.

Exploration of the immunomodulatory activities of the multifunctional cytokine interleukin-11 (IL-11) has prompted several therapeutic applications. The immunomodulatory effects of IL-11 on human antigen-presenting cells and on T cells were investigated. IL-11 inhibited IL-12 production by activated CD14+monocytes, but not by mature dendritic cells (DCs) stimulated via CD40 ligation. Moreover, IL-11 did not affect either DC maturation, as demonstrated by phenotypic analysis and evaluation of cytokine production, or DC generation from progenitor cells in the presence of specific growth factors. Molecular analysis demonstrated the expression of IL-11 receptor messenger RNA in highly purified CD14+monocytes, CD19+B cells, CD8+, and CD4+T cells, and CD4+CD45RA+naive T lymphocytes. In keeping with this finding, IL-11 directly prevented Th1 polarization of highly purified CD4+CD45RA+naive T cells stimulated with anti-CD3/CD28 antibodies, as demonstrated by significant increases of IL-4 and IL-5, by significantly decreased interferon-γ production and by flow cytometry intracellular staining of cytokines. Coincubation of naive T cells with DCs, the most potent stimulators of Th1 differentiation, did not revert IL-11–mediated Th2 polarization. Furthermore, parallel experiments demonstrated that the activity of IL-11 was comparable with that induced by IL-4, the most effective Th2-polarizing cytokine. Taken together, these findings show that IL-11 inhibits Th1 polarization by exerting a direct effect on human T lymphocytes and by reducing IL-12 production by macrophages. Conversely, IL-11 does not exert any activity on DCs. This suggests that IL-11 could have therapeutic potential for diseases where Th1 responses play a dominant pathogenic role.

Here we review our recent experience addressing the issue of positive selection and transplantation of hematopoietic CD34+ cells to reduce neoplastic contamination in peripheral blood (PB) autografts from patients with multiple myeloma (MM). We evaluated PB samples from 30 pretreated MM patients following the administration of high dose cyclophosphamide (Cy; 7g/m2 or 4g/m2) and granulocyte-colony stimulating factor (G-CSF), for collection of circulating stem cells (PBSC) to support hematopoietic reconstitution following myeloablative radio-chemotherapy.Twenty six patients showed adequate mobilization of CD34+ progenitor cells and were submitted to PBSC collection. Circulating hematopoietic CD34+ cells were highly enriched by avidin-biotin immunoabsorption, cryopreserved, and used to reconstitute BM function after myeloablative therapy in 13 patients. The median purity of the enriched CD34+ cell population was 89.5% (range 51-94%) with a 75-fold increase compared to the pretreatment samples. The median overall recovery of CD34+ cells and CFU-GM was 58% (range 33-95%) and 45% (range 7-100%). respectively. Positive selection of CD34+ cells resulted in 2.5-3 log of plasma cells and CD 19+ B-lineage cells depletion as determined by immunofluorescence studies, although DNA analysis of CDR III region of IgH gene demonstrated the persistence of minimal residual disease (MRD) in 5 out of 6 patient samples studied. Myeloma patients were reinfused with enriched CD34+ cells after myeloablative therapy consisting of total body irradiation (TBI, 1000 cGy) and high dose Melphalan (140 mg/m2) or Melphalan (200 mg/m2) alone. They received a median of 5 × 106 CD34+ cellskg and showed a rapid reconstitution of hematopoiesis: the median time to 0.5 × 109 neutrophils, 20 and 50 × 109 plateletsk of PB was 10, 11 and 12 days, respectively. When we analyzed the immunological reconstitution of this group of patients, we observed a rapid and full recovery of total lymphocyte and NK cell count, although the absolute CD4+ cell count was lower than pretreatment level. These results, as well as other clinically significant parameters, did not significantly differ from those of patients (=13) receiving unmanipulated PBSC following the same pretransplant conditioning regimen. The results of this trial demonstrate that positive selection of CD34+ cells reduces the contamination of myeloma cells from the apheresis products up to 3 log and provides a cell suspension capable of restoring a normal hematopoiesis after a TBI-containing conditioning regimen. Based on this pilot trial, we have recently started a clinical study involving a double autotransplant, conditioned with melphalan (200 mg/m2) followed by melphalan (140 mg/m2) and busulphan (14 mg/kg). supported by the reinfusion of highly purified CD34+ cells.