Donor Selection in HLA-Mismatched Hematopoietic Stem Cell Microtransplantation for Acute Myeloid Leukemia

Expert consensus on microtransplant for acute myeloid leukemia in elderly patients -report from the international microtransplant interest group

Recent studies have shown that microtransplant (MST) could improve outcome of patients with elderly acute myeloid leukemia (EAML). To further standardize the MST therapy and improve outcomes in EAML patients, based on analysis of the literature on MST, especially MST with EAML from January 1st, 2011 to November 30th, 2022, the International Microtransplant Interest Group provides recommendations and considerations for MST in the treatment of EAML. Four major issues related to MST for treating EAML were addressed: therapeutic principle of MST (1), candidates for MST (2), induction chemotherapy regimens (3), and post-remission therapy based on MST (4). Others included donor screening, infusion of donor cells, laboratory examinations, and complications of treatment.

Cord blood stem cell-generated KIR+NK cells effectively target leukemia cell lines

Acute lymphoid (ALL) and myeloid leukemia (AML) are known to be invasive and highly lethal hematological malignancies. Because current treatments are insufficient and have a variety of side effects, researchers are looking for new and more effective therapeutic methods. Interestingly, ongoing efforts to find the best approach to optimize NK cell anti-leukemia potential shed light on the successful treatment of cancer. Mature KIR⁺NK cells ability to remove HLA Class-I deficient cells has been exploited in cancer immunotherapy. Here, we generated KIR⁺NK cells from cord blood stem cells using IL-2 and IL-15 cytokines. Our finding underlined the importance of KIR expression in the cytotoxic function of NK cells. Taken together, this study presented an effective in vitro method for the expansion and differentiation of KIR⁺NK cells using cytokines without any feeder cells. Furthermore, the presented culture condition could be useful for the generation of mature and pure NK cells from limited numbers of CD34⁺ cord blood cells and might be used as a novel method to improve the current state of cancer therapy.

Case report: Rare persistent complete donor chimerism and GVHD following micro-transplantation from HLA haplotype homozygous donors

HLA-mismatched hematopoietic stem cell micro-transplantation (MST) is an effective treatment for older patients (≥60 years) with acute myeloid leukemia. Donor selection for MST is broad, ranging from HLA fully mismatched unrelated donors to HLA partially matched related donors. However, the influence of HLA haplotype homozygous donors such donors on MST has not been studied. Such donors has been reported to be associated with a higher risk of graft-versus-host disease (GVHD) in transfusion and cord blood transplantation (CBT). Additionally, sustained complete donor chimerism is rare in MST and usually accompanied by severe acute GVHD and death. Herein, we report the first case of MST using an HLA haplotype homozygous donor. The patient developed persistent complete donor chimerism (donor cells>95%) for 7 months and prolonged isolated thrombocytopenia (PT) for 3 months, after receiving MST from his HLA homozygous son. Grade I acute GVHD presented on day 12 post-MST and it was controlled by timely immunosuppressive treatment. Then he maintained complete molecular remission, complete donor chimerism and mild GVHD for 5 months. However, moderate overlapping GVHD with skin, oral, eyes, and intestinal involvement developed after he self-discontinued Tacrolimus treatment. Fortunately, the GVHD was controlled after intensive anti-rejection therapy and Tacrolimus is now being continued for prophylaxis. This case underscores that HLA haplotype homozygous donors might not be a good choice for MST and GVHD prophylactic should be administrated if such donors have to be selected.

The role of KIR positive NK cells in diseases and its importance in clinical intervention

Natural killer (NK) cells are essential for the elimination of the transformed and cancerous cells. Killer cell immunoglobulin-like receptors (KIRs) which expressed by T and NK cells, are key regulator of NK cell function. The KIR and their ligands, MHC class I (HLA-A, B and C) molecules, are highly polymorphic and their related genes are located on 19 q13.4 and 6 q21.3 chromosomes, respectively. It is clear that particular interaction between the KIRs and their related ligands can influence on the prevalence, progression and outcome of several diseases, like complications of pregnancy, viral infection, autoimmune diseases, and hematological malignancies. The mechanisms of immune signaling in particular NK cells involvement in causing pathological conditions are not completely understood yet. Therefore, better understanding of the molecular mechanism of KIR-MHC class I interaction could facilitate the treatment strategy of diseases. The present review focused on the main characteristics and functional details of various KIR and their combination with related ligands in diseases and also highlights ongoing efforts to manipulate the key checkpoints in NK cell-based immunotherapy.