Successful allogeneic haematopoietic stem cell transplantation (HCT) requires a rapid recovery of haematopoiesis and NK-cell cytotoxicity. The aim of our study was to investigate a dynamic of this recovery in 35 patients who underwent HCT in the very first weeks after transplantation. Samples of peripheral blood were investigated in 6 weeks intervals starting from the day +16 until the release of a patient from hospital to outpatient care (the day +38). Flow cytometry to investigate subpopulations of leucocytes and nonradioactive Europium release assay using K562 cell line as target cells to appreciate NK-cell cytotoxicity were used. TheNK-cell cytotoxicity reached the level of healthy persons on average in the day +22. No statistically significant differences in the recovery of CD3+, CD4+, CD8+ and CD56+ cells were observed when the group of transplanted patients suffering from acute graft versus host disease (GvHD) was compared to that with no signs of post-transplant immune reactions. A significantly higher percentage of CD8+ cells were found in the GvHD group of patients on the day +22 (p = 0.009) and +28 (p = 0.03), respectively compared the non-GvHD group of patients; however, differences in the NK-cell cytotoxicity did not reach statistical significance. By comparing recipients receiving a bone marrow with those transplanted with peripheral blood stem cells, a statistically significant faster recovery of theNK-cell cytotoxicity was observed on the day +16 after transplantation.

        Key words: blood and immune cells recovery, graft versus host disease, haematopoietic stem cell transplantation, NK-cell cytotoxicity