Mesenchymal stem cells (MSC) are characterized by tolerogenic potential and therefore, are used in the treatment of autoimmune diseases such as graft-versus-host disease (GVHD) reactions after allogeneic hematopoietic cell transplantation to improve the transplant functions, as well as for the therapy and prevention of cytokine storm in COVID-19 patients and some other conditions. However, MSC can exhibit proinflammatory activity, which causes risks for their clinical use. We studied the cytokine profile of bone marrow MSC culture and demonstrate intensive production of IL-6, IL-8, and chemokine MCP-1, which participate in the pathogenesis of cytokine storm and GVHD. At the same time, no anti-inflammatory IL-4 and IL-10 were detected. To reduce the risks of MSC application in the GVHD therapeutic protocols, further studies of the conditions promoting generation of MSC with tolerogenic potential and approved clinical standards of MSC use are required.

The potential of mesenchymal multipotent (stem) cells (MSC) to modify immune reactions and mediate hematopoiesis boosted great interest for their use in allogeneic hemopoietic stem cell transplantation. Because of MSC production of a wide range of cytokines and growth factors, these cells are included in the therapy of graft-versus-host disease (GVHD). A number of clinical studies have demonstrated safety and efficacy of MSC-based therapy in acute GVHD. Japan and some other countries approved biomedical cell products on the base of allogeneic bone marrow (BM) MSCs as medical agents for acute GVHD treatment. Besides, MSCs may form BM stroma and improve hematopoiesis. Simultaneous transplantation of hematopoietic stem cells and MSCs effectively improved engraftment and prevented GVHD in transplantation of umbilical cord blood and human leukocyte antigens-incompatible BM stem cells. The review presents the analysis of clinical studies of MSCs in allogeneic hematopoietic stem cell transplantation and discusses different approaches for improvement of MSC-based GVHD treatment and prophylaxis.

Conditioning regimens prior to hematopoietic stem cell transplantation (HSCT) are often accompanied by a period of aplasia characterized by severe neutropenia, anemia, and thrombocytopenia. Long-term antibacterial and immunosuppressive therapy in patients with graft-versus-host disease (GVHD) exacerbates hematopoietic depression. Colony-stimulating factors, erythropoietins, and thrombopoietin receptor agonists are used to correct hematological dysfunction in these patients. However, these drugs have side effects, and their stimulating effect, as a rule, is limited to one of the hematopoietic lineages. At the same time, in patients after HSCT, for the prevention and treatment of hematopoietic disorders against the background of GVHD, it is necessary to use drugs that promote the restoration of all hematopoietic cell lines. Inducers of Toll- and NOD-like receptors, stimulators of emergency hematopoiesis, can be considered as promising drugs for this category of patients. These compounds include bacterial derivatives and sulfated poly(oligo)saccharides capable of stimulating hematopoiesis, which allows us to consider them as promising stimulants of hematopoiesis for the treatment and prevention of disorders of the immune status and hematopoiesis in GVHD.

Fanconi anemia (AF) is a hereditary genetic disease characterized by developmental abnormalities, progressive bone marrow failure, hypersensitivity to alkylating agents, and a tendency to hematological and solid tumors throughout life. The only curative option in the treatment of bone marrow failure in patients with AF is allogeneic hematopoietic stem cell transplantation (allo-HSCT). There are no detailed descriptions of allo-HSCT in patients with AF in the Russian-language literature. On the example of a clinical case with AF at the onset of myelodysplastic syndrome, a choose of method for treating bone marrow failure is presented.

COVID-19 is a real challenge for the protective immunity. Some people do not respond to vaccination by acquiring an appropriate immunological memory. The risk groups for this particular infection such as the elderly and people with compromised immunity (cancer patients, pregnant women, etc.) have the most serious problems in developing an adequate immune response. Therefore, dendritic cell (DC) vaccines that are loaded ex vivo with SARS-CoV-2 antigens in the optimal conditions are promising for immunization. Lymphocyte effector cells with chimeric antigen receptor (CAR lymphocytes) are currently used mainly as anti-tumor treatment. Before 2020, few studies on the antiviral CAR lymphocytes were reported, but since the outbreak of SARS-CoV-2 the number of such studies has increased. The basis for CARs against SARS-CoV-2 were several virus-specific neutralizing monoclonal antibodies. We propose a similar, but basically novel and more universal approach. The extracellular domain of the immunoglobulin G receptors will be used as the CAR receptor domain. The specificity of the CAR will be determined by the antibodies, which it has bound. Therefore, such CAR lymphocytes are highly universal and have functional activity against any infectious agents that have protective antibodies binding to a foreign surface antigen on the infected cells.