HLA-haploidentical hematopoietic stem cells transplantation with regulatory and conventional T-cell adoptive immunotherapy in pediatric patients with very high-risk acute leukemia.

Allogeneic hematopoietic stem cell transplantation (HSCT) is still needed for many children with very high-risk acute leukemia. An HLA-haploidentical family donor is a suitable option for those without an HLA-matched donor. Here we present outcomes of a novel HLA-haploidentical HSCT (haplo-HSCT) strategy with adoptive immunotherapy with thymic-derived CD4+CD25+ FoxP3+ regulatory T cells (Tregs) and conventional T cells (Tcons) performed between January 2017 and July 2021 in 20 children with high-risk leukemia. Median age was 14.5 years (range, 4-21), 15 had acute lymphoblastic leukemia, 5 acute myeloid leukemia. The conditioning regimen included total body irradiation (TBI), thiotepa, fludarabine, cyclophosphamide. Grafts contained a megadose of CD34+ cells (mean 12.4 × 106/Kg), Tregs (2 × 106/Kg) and Tcons (0.5-1 × 106/Kg). All patients achieved primary, sustained full-donor engraftment. Only one patient relapsed (5%). The incidence of non-relapse mortality was 15% (3/20 patients). Five/20 patients developed ≥ grade 2 acute Graft versus Host Disease (aGvHD). It resolved in 4 who are alive and disease-free; 1 patient developed chronic GvHD (cGvHD). The probability of GRFS was 60 ± 0.5% (95% CI: 2.1-4.2) (Fig. 6), CRFS was 79 ± 0.9% (95% CI: 3.2-4.9) as 16/20 patients are alive and leukemia-free. The median follow-up was 2.1 years (range 0.5 months-5.1 years). This innovative approach was associated with very promising outcomes of HSCT strategy in pediatric patients.

Selection of a panel of monoclonal antibodies for monitoring residual disease in peripheral blood and bone marrow of interferon-treated hairy cell leukaemia patients.

A panel of monoclonal antibodies (mAbs) directed against B-cell and hairy cell leukaemia (HCL)-associated antigens was used to identify residual hairy cells in the peripheral blood and/or bone marrow samples from 20 patients with HCL, following treatment with interferon-alpha (IFN-alpha) or interferon-beta (IFN-beta). In all cases, hairy cells retained their characteristic phenotype, e.g. positivity for CD22, CD11c, CD25, CD32, and the HCL-associated trimeric protein (t-GP) recognized by the mAbs HML-1, B-ly7, LF61 and Ber-Act8. The most specific marker for identifying a small percentage of hairy cells in peripheral blood cytospins, was t-GP. In alkaline phosphatase/anti alkaline phosphatase (APAAP) stained preparations, t-GP+ hairy cells (provided with large cytoplasm and hairy surface) could be usually distinguished from t-GP+ normal lymphocytes (small-sized cells with smooth surface). In doubtful cases the percentage of residual hairy cells could exactly be estimated by double immunofluorescence staining for CD22 (B-cell marker) and t-GP. The rationale of the test is based on the finding that the small percentage (about 1%) of t-GP+ lymphocytes circulating in the peripheral blood of normal individuals are T-cells of the CD8 subset and not B-cells. The best markers for identifying residual hairy cells in routine bone marrow biopsies were CD45RA (mAb 4KB5) and CD20 (mAb L26). Immunohistological labelling was superior to morphological examination in picking up scattered hairy cells in bone marrow biopsies showing either severe hypoplasia or exuberant hyperplasia of normal haemopoietic series.

Variable expression of leucocyte-common (CD45) antigen in CD30 (Ki1)-positive anaplastic large-cell lymphoma: implications for the differential diagnosis between lymphoid and nonlymphoid malignancies.

Monoclonal antibodies (mAbs) directed against the leucocyte common (CD45) antigen have been proposed as a useful tool for the differential diagnosis between malignant lymphomas (CD45+) and poorly differentiated nonhemopoietic tumors (CD45-). Thanks to the availability of mAbs directed against fixative-resistant epitopes of the CD45 molecule, this distinction can now easily be made even in routinely processed tissues. However, a small percentage of morphologically poorly defined neoplasms are difficult to diagnose even with the help of immunohistochemistry. The investigators report that 63 out of 165 anaplastic large-cell (ALC) lymphomas did not show any reactivity for the CD45 antigen in paraffin sections. In routine biopsies, the lymphomatous nature of these cases, most of which had been sent for consultation, could be always unequivocally established by demonstrating negativity for cytokeratins (mAb KL1) and clear dot-like and/or surface reactivity with the Ber-H2 mAb, which is directed against a fixative-resistant epitope of the lymphoid cell activation antigen CD30. Strikingly, 54% of the CD45-cases reacted with mAbs directed against fixative-resistant epitopes of the T cell-restricted CD45RO antigen (mAb UCHL1) or the B-restricted molecules CD45RA (mAb 4KB5) and L26 (unclustered). In order to avoid confusion of ALC lymphomas with anaplastic nonlymphoid tumors, pathologists must be aware of the existence of CD30+/CD45- ALC lymphomas, as they can mimic the above-mentioned malignancies both morphologically (due to the sinusoidal growth pattern) and phenotypically (due to the expression of EMA). The investigators conclude that the combined use of mAbs directed against fixative-resistant epitopes of the CD30, CD45RO, CD45RA, and L26 antigens and cytokeratins is essential for the correct diagnosis and treatment of these equivocal cases.

Large cell lymphoma of bone. A report of three cases of B-cell origin.

Clinicopathological and immunohistological features of three cases of large cell lymphoma of bone are reported. On histological grounds, all the cases were diagnosed as histiocytic lymphomas (Rappaport) or primary centroblastic lymphomas, polymorphic subtype (Kiel). On immunophenotyping, malignant cells strongly reacted with the anti-leucocyte antibodies PD7/26 and ROS-220C, thereby indicating their lymphomatous nature, and expressed the B-cell antigens CD19 and CD22. Further studies are warranted to determine whether the B-cell phenotype observed in our cases is typical of the majority of primary large cell lymphomas of bone. Immunohistological analysis with monoclonal antibodies is expected to be of great value not only in defining the immunological phenotype of this rare pathological entity, but also in differentiating it from other neoplasms that involve the skeleton, either primarily or secondarily.

Expression of lymphoid-associated antigens on Hodgkin's and Reed-Sternberg cells of Hodgkin's disease. An immunocytochemical study on lymph node cytospins using monoclonal antibodies.

The aim of this study was to elucidate the origin of Hodgkin's and Reed-Sternberg cells. Lymph node cytospins and frozen sections from 20 cases of Hodgkin's disease of different histological subtypes were immunostained by the immuno-alkaline phosphatase technique using a panel of monoclonal antibodies. As expected, the Hodgkin's and Reed-Sternberg cells of all cases were positive for the CD30 (Ki-1), CD15 (hapten X) and CD25 (Tac) antigens. In eight cases, a variable percentage of typical Hodgkin's and Reed-Sternberg cells showed a clear-cut cytoplasmic and/or surface positivity for the T-cell-associated antigens CD3, CD5, CD6 and CD4 (seven cases) or CD8 (one case), but consistently lacked B-cell and macrophage-associated markers. The best visualization of T-cell antigens was obtained in cytocentrifuge preparations and in areas of lymph node frozen sections that had been infiltrated by clusters of Hodgkin's and Reed-Sternberg cells. In two cases of Hodgkin's disease (nodular sclerosis, mixed cellularity) the neoplastic cells weakly expressed the B-cell antigens CD19 and CD22, but not T-cell or macrophage-associated markers. In 10 cases, Hodgkin's and Reed-Sternberg cells were negative for all the lymphoid- and macrophage-associated antigens. These results suggest a lymphoid (either T or B) rather than histiocytic origin for the Hodgkin's and Reed-Sternberg cells in a number of Hodgkin's disease cases.