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P Sedlácek

Publications and source records attributed to P Sedlácek.

At least 19 recordsLinked to original sources
PubMed2006

Low mortality of children undergoing hematopoietic stem cell transplantation from 7 to 8/10 human leukocyte antigen allele-matched unrelated donors with the use of antithymocyte globulin.

Human leukocyte antigen (HLA)-matched sibling donor hematopoietic stem cell transplantation (HSCT) is available for only approximately 30% patients needing HSCT. Use of alternative donors is associated with a high incidence and severity of graft-versus-host disease (GVHD). Here we report our experience with GVHD prophylaxis using pre-transplant rabbit antithymocyte globulin (rATG), in addition to post transplant cyclosporin A and methotrexate. Seventy-five children received unmanipulated grafts from 7 to 10/10 HLA allele-matched unrelated donors. Median follow-up was 25 months (range, 6-65 months). Only 2/75 patients (2.5%) developed acute GVHD grades III-IV, and 17/75 (25%) developed extensive chronic GVHD. Overall survival was 79%. It was similar in patients receiving grafts from 7 or 8/10 to 9 or 10/10 allele-matched donors, and similar in patients receiving peripheral blood stem cells and marrow. Six (11%) patients died owing to relapse, and 10 (13%) due to transplant-related complications. The addition of rATG appears to result in a low incidence of severe GVHD and overall mortality.

Adolescent↗
PubMed2006

[Familial haemophagocytic lymphohistiocytosis caused by perforin deficit can be successfully treated by haematopoietic stem cell transplantation--the first diagnosed case in the Czech Republic].

Familial haemophagocytic lymphohistiocytosis (FHL) is an inherited disorder characterized by an impaired cytotoxicity of T lymphocytes and NK cells typically manifesting within first few months after birth. If not treated adequately, it is inevitably fatal within several months. The incidence in Caucasians has been estimated to 1: 50 000 births. Haematopoietic stem cell transplantation represents the only curative treatment for FHL. Recently, several genetic defects underlying molecular defects in FHL have been identified. In approximately 30% of patients FHL is caused by mutations in PRF1 gene coding for perforin. Further 30% of patients were found to have mutations in UNC13D coding for hMunc13-4 protein. Very recent report has identified another cause of FHL, mutations in STX11 gene on chromosome 6, coding for syntaxin 11. Absence of any of those proteins severely impairs the process of exocytosis of cytotoxic granules. We describe patient with clinical symptoms of FHL. Immunological and molecular biology methods led to the identification of perforin mutation as a cause of the disease. Patient received an allogeneic SCT from HLA-matched unrelated donor. SCT was followed by rapid normalization of clinical symptoms and laboratory findings. In patient described in this study, FHL manifested with typical clinical and laboratory symptoms. Adequate immunosuppressive treatment and subsequent SCT led to the sustained remission of FHL and correction of molecular defect. This is the first case of FHL in Czech Republic where perforin mutation was identified as a molecular cause both at cellular and molecular level.

Female↗
PubMed2006

[HLA-DPB1 gene analysis in haematopoietic stem cell transplantations].

BACKGROUND: The HLA-DPB1 gene is probably one of HLA class II genes affecting the haematopoietic stem cell transplantation. The aim of the study was to analyse the HLA-DPB1 gene and its match/mismatch in patients transplanted from unrelated HSC donors. The PCR-SSP method was used for the typing of the HLA system. METHODS AND RESULTS: The cohort consisted of 201 pairs of patient/unrelated HSC donor. Match in HLA-A, -B, -Cw, -DRBI and -DQBI (e.g. 10/10 match) was found in 81 pairs. The HLA-DPBI was tested in them. 18 different HLA-DPBI alleles were identified in this cohort. Complete match (e.g.12/12) was detected in 3% of the 201 analysed pairs only. CONCLUSIONS: The probability of finding 12/12 matching unrelated HSC donor is limited due to the high percentage of mismatches and inaccessibility of previous HLA-DPB1 results.

Adult↗
PubMed2006

[EBV quantification in children after allogeneic hematopoietic stem cell transplantation].

BACKGROUND: Patients undergoing allogeneic hematopoietic stem cell transplantation (AHSCT) are endangered by developing Epstein-Barr virus-related post-transplant lymfoprolipherative disease (EBV-LPD). The aims of the study were to retrospectively characterise the viral loads in four patients who died of this complication, and to test possible risk factors for EBV reactivation in a prospectively observed cohort of children after AHSCT. METHODS AND RESULTS: Serial DNA samples extracted from whole blood from four patients who died of post-transplant EBV-LPD in year 2000 were retrospectively analysed for EBV load using quantitative real-time PCR. First detection of EBV activation preceded death by 24-91 days. All four patients exceeded a viral load of one million EBV copies per 100,000 human genome equivalents. A cohort of 72 children undergoing AHSCT between 2001-2004 was prospectively followed-on using the same quantification method from regularly obtained samples of whole blood, and clinical and laboratory data were recorded on a weekly basis, totalling at 3,896 person-weeks of observation. Approximately one half of the cohort experienced at least one episode of EBV reactivation during the first 100 days after AHSCT, four of the episodes being accompanied with viral loads higher than our provisional threshold of 10,000 copies per 100,000 human genome equivalents. Three of the four patients developed EBV-LPD and were successfully treated by intravenous administration of anti-CD20 antibody. Testing of possible clinical and laboratory predictors of EBV reactivation did not reveal any clinically useful association. CONCLUSIONS: The cornerstone of predicting EBV-LPD in AHSCT is a regular monitoring of EBV viral load using quantitative methods. Using this strategy with a threshold of 10,000 EBV copies per 100,000 human genome equivalents was proved to be effective, as shown by no death of EBV for the study period, compared to four cases in the year before the quantitative monitoring.

Child↗
PubMed2004

[Consolidation of therapy of acute myeloid leukemia with the AML-BFM 93 protocol in children in the Czech Republic].

BACKGROUND: Acute myeloid leukemia (AML) in children is rare. Although more resistant to chemotherapy than acute lymphoblastic leukemia, its responsiveness and survival rates have considerably improved during the last 15 years by virtue of intensification of chemotherapy and due to the better supportive care. Relapses still remain the main cause of treatment failure. Management of children with AML was unified in the Czech Republic in 1993 according to AML-BFM 93 Study protocol. METHODS AND RESULTS: Treatment results were evaluated in 61 patients, of whom 45 (73.8%) achieved complete remission. Five-year event-free-survival (EFS) was found in 42.3%, and overall survival was 45.3%. Prognosis of the standard-risk patients was significantly better than in the high-risk group (EFS 62.5% vs. 29.7%, p = 0.03). The most important prognostic factor was the early treatment response. Compared to chemotherapy, allogeneic stem-cell transplantation did not significantly improve the outcome of high-risk patients. CONCLUSIONS: Treatment results of children with AML in the Czech Republic are comparable to those achieved by leading leukemia study groups in the world. The aim of the next study is to increase the complete-remission rate by reducing early deaths.

Acute Disease↗
PubMed2002

[Transplantation of highly purified CD34+ hematologic peripheral stem cells from haploidentical related donors in the treatment of children with non-malignant diseases].

BACKGROUND: Children suffering from rare inherited disorders can be cured using stem cell transplantation (SCT). For patients where HLA-identical donor could not be found, there is an excellent chance of identifying a family member who shares an identical haplotype with the patient but whose second haplotype is different. This situation is called an HLA-full haplotype mismatch. Risks of haploidentical transplantation are graft rejection and severe graft-versus-host disease (GVHD). Histocompatibility barriers can be overcome by infusing high doses of T-cell depleted peripheral CD34+ stem cells. METHODS AND RESULTS: Between December 1995 and March 2000, 5 children with rare inherited disorders were transplanted using highly purified CD34+ stem cells from haploidentical parents at the 2nd Department of Pediatrics, University Hospital Motol, Prague. Two children suffered from severe combined immunodeficiency (SCID), one child from malignant osteopetrosis, Wiskott-Aldrich syndrome and hemophagocytic lymphohistiocytosis, respectively. Positive selection of peripheral CD34+ stem cells from G-CSF stimulated donors was performed using the method of immunoabsorbtion (CellPro) (n = 2) or immunomagnetic separation (CliniMACS) (n = 3). Donor type engraftment was achieved in 4 children. In one of them early graft failure has developed successfully managed by second SCT from the same donor. One child with SCID had primary graft failure. Mild acute GVHD with good response to steroid therapy developed in 2 children. Three children are alive and 2 of them are cured. Two children died due to post-transplant complications--CMV pneumonia and encephalitis. CONCLUSIONS: Transplantation of highly purified CD34+ stem cells from haploidentical parents is a reasonable therapeutic option for children with some specific nonmalignant disorders lacking HLA identical donor. Risks of this type of SCT are the graft failure and severe infectious complications due to slow immunological reconstitution in comparison with SCT from HLA identical donors.

Antigens, CD34↗
PubMed2002

Real-time quantitative PCR detection of WT1 gene expression in children with AML: prognostic significance, correlation with disease status and residual disease detection by flow cytometry.

The clinical significance of WT1 gene expression at diagnosis and during therapy of AML has not yet been resolved. We analysed WT1 expression at presentation in an unselected group of 47 childhood AML patients using real-time quantitative reverse-transcription PCR. We also showed that within the first 30 h following aspiration RQ-RT-PCR results were not influenced by transportation time. We observed lower levels of WT1 transcript in AML M5 (P = 0.0015); no association was found between expression levels and sex, initial leukocyte count and karyotype-based prognostic groups. There was significant correlation between very low WT1 expression at presentation and excellent outcome (EFS P = 0.0014). Combined analysis of WT1 levels, three-colour flow cytometry residual disease detection and the course of the disease in 222 samples from 28 children with AML showed remarkable correlation. Fourteen patients expressed high WT1 levels at presentation. In eight of them, who suffered relapse or did not reach complete remission, dynamics of WT1 levels clearly correlated with the disease status and residual disease by flow cytometry. We conclude that very low WT1 levels at presentation represent a good prognostic factor and that RQ-RT-PCR-based analysis of WT1 expression is a promising and rapid approach for monitoring of MRD in approximately half of paediatric AML patients.

Acute Disease↗
PubMed2002

Cytotoxic T lymphocyte precursor frequency analysis in the selection of HLA matched unrelated donors for hematopoietic stem cell transplantation: the correlation of CTLp frequency with HLA class I genotyping and aGVHD development.

The selection of human leukocyte antigen (HLA) compatible unrelated donors for hematopoietic stem cell transplantation (HSCT) is based on the direct genotyping of HLA class I and class II alleles (HLA-A, -B, -C, -DRB1, -DQB1 loci). The cellular test estimating the frequency of cytotoxic T lymphocyte precursors (CTLp) has been included into the selection procedure of unrelated donors to detect the class I alloreactivity and to predict acute graft versus host disease (aGVHD) occurrence and severity. The relationship between HLA-A, -B, -C high/medium resolution genotyping and CTLp activation was analysed in the cohort of 78 unrelated donor/patient pairs indicated for HSCT. The high frequency of CTLp (> 1:100,000) correlated significantly (p < or = 0.0002) with the incompatibilities in alleles of HLA-A, -B, -C loci. Nevertheless, the results of HLA-A, -B, -C genotyping and CTLp assay are not fully alternative, suggesting that the CTLp test gives its specific information. The high CTLp frequency (CTLpf) in 14/35 pairs fully matched by HLA class-I alleles genotyping could reflect the influence of another factors upon the CTLp activation. On the contrary, the low CTLp frequency values (< or = 1:100,000) found in 8/43 pairs with existing HLA class-I alleles incompatibilities could indicate the immunological permissivity of these particular mismatches. The clinical relevance of the CTLp test for aGVHD prediction has been also analysed. The relationship between CTLp activation in vitro and the incidence and severity of aGVHD was evaluated in 37 patients who underwent allogeneic HSCT. The severe form of aGVHD (grade III-IV) developed in 9 of 18 cases (50%) with the high pretransplant CTLpf value. The patients with the low CTLpf (n = 19) suffered from the severe form of aGVHD in 2 cases (10%) only, the remaining 17 patients from this group were without aGVHD symptoms or developed only the mild form of aGVHD (I-II). The relationship between CTLp results and the incidence and severity of aGVHD was found statistically significant (p < or = 0.01).

Genes, MHC Class I↗
PubMed2001

[A method for modeling skin explants--an in vitro predictive test for graft vs host disease in allogenic hematopoietic cell transplantation].

BACKGROUND: Acute graft versus host disease (GvHD) remains a severe complication of allogeneic haematopoietic stem cell transplantation (HSCT). Our study summaries results of skin explant assay (SEA) as a pretransplant GvHD predictive test in a cohort of paediatric (n = 33) and adult (a = 8) patients receiving grafts from their HLA identical siblings (n = 28), haploidentical relatives (n = 3) and unrelated donors (n = 10). Results GvHD prediction are correlated with the occurrence and severity of acute GvHD posttransplant and effect of GvHD prophylaxis on GvHD clinical outcome is evaluated. METHODS AND RESULTS: SEA utilises responding lymphocytes of the donor, which are sensitized firstly in vitro by mononuclears cells of patient in allogeneic mixed lymphocyte culture (MLC) and subsequently co-cultured with recipient's skin. Histopathological changes found in patients' skin explants are evaluated according to standard Lerner classification for acute GvHD. In general, GvHD predictive results in SEA correlated with GvHd clinical outcome in 28 out of 41 tested patients (68%, p = 0.015). In a cohort of HLA identical sibling transplants GvHD predictive results correlated with clinical manifestation of acute GvHD only in 15 out of 28 patients on individual GvHD prophylaxis. GvHD prophylaxis in the form of cyclosporine A (CsA) combined with short-term methotrexate (MTX) reduced the risk of acute GvHD in 10 out of 14 transplanted patients (71%) meanwhile CsA alone prophylaxis only in 1 out of 5 patients (20%). In a cohort of unrelated pairs on CsA/MTX prophylaxis combined with horse anti-lymphocyte globuline (ALG) correlated the GvHD prediction with GvHD clinical outcome (100%, p = 0.003). In all patients transplanted with the grafts from their haploidentical relatives the occurrence of severe GvHD was predicted. CONCLUSION: Skin explant assay helps identify pretransplant patients at higher risk of severe acute GvHD. GvHD predictive results enable the transplantation team to individualise GvHD prophylaxis and to optimise selection of the donor.

Acute Disease↗
PubMed2001

Loss of heterozygosity and heterogeneity of its appearance and persisting in the course of acute myeloid leukemia and myelodysplastic syndromes.

Screening for loss of heterozygosity (LOH) of the panel of 18 highly polymorphic microsatellite markers, especially from the region 11p15, was carried out on 154 samples from 26 patients with acute myeloid leukemia and eight with myelodysplastic syndromes (MDS). LOH was detected at the majority (72%) of the loci tested: 47% of informative patients displayed LOH for at least one of the microsatellite locus from the region 11p15 and 23.5% of patients displayed LOH among the other markers tested within the study. A longitudinal follow-up of patients showed a remarkable heterogeneity of LOH appearance and its persistance during the course of the disease suggesting an intratumor clonal heterogeneity, or alternatively, presence of LOH in more than one cell clone. The data revealed two regions of high loss of one allele in 11p15.5, defined by markers D11S1363 and D11S1338, indicating that LOH at the subtelomeric region of the short arm of chromosome 11 is a much common event in hematological malignancies than it was previously reported.

Adolescent↗
PubMed2001

Hematopoietic stem cell transplantation in children with hematological malignancies across HLA barriers--reasonable alternative?

The aim of this study was to evaluate the efficiency and risks of T-cell depletion in prevention of graft versus host disease (GVHD) using HLA haploidentical family donors as an alternative source of hematopoietic stem cells (HSC) in children with hematological malignancies without suitable matched donor. Ten children, median age 12 years (range, 3-17), were transplanted from haploidentical family donors for acute lymphoblastic leukemia (n = 4), acute myelogenous leukemia (n=2), chronic myelogenous leukemia (n = 2), non-Hodgkin lymphoma (n = 1) and myelodysplastic syndrome (n = 1). Parents were donors for nine, sibling for one patient. T-cell depletion of HSC was performed using CellPro followed by antiCD2/CD3 depletion in 7, and CliniMacs magnetic sorting in 3 grafts. Primary engraftment was achieved in nine patients. Patient with graft failure was successfully re-grafted. Primary acute GVHD was diagnosed in one patient who got higher amount of T-cells in the graft. Secondary GVHD was induced by add-backs of lymphocytes in four patients. Three patients developed chronic GVHD. Four patients died due to transplant related mortality (40%), one from veno-occlusive disease, two due to CMV pneumonia and one of aspergillosis with extensive chronic GVHD. Four patients relapsed with leukemia within 35-98 days post transplant, three without previous signs of GVHD, and all died. Two patients are alive and well 26 and 42 months after transplant. Haploidentical family donors appear to be a reasonable alternative option for patients with urgent indications for allogeneic transplant and/or without a matched donor.

Adolescent↗
PubMed2001

Comparison of two different methods for CD34+ selection and T cell depletion in peripheral blood stem cell grafts--our experiences with CellPro, E rosetting and CliniMACS technique.

The aim of this study was to establish a suitable method for in vitro T cell depletion in peripheral blood stem cell grafts for mismatched/haploidentical transplantation in children and adults with severe hematological disorders and for autologous transplantation in patients with autoimmune diseases refractory to conventional immunosuppressive treatment. Two different selection techniques have been used: CD34+ selection using immunoaffinity columns (CellPro Ceprate) followed by T cell depletion by E-rosetting or CD34+ selection using submicroscopic paramagnetic beads (CliniMACS device) with T cell depletion in a one step procedure. The mean purity and recovery of CD34+ cells and efficiency of T cell removal in the final product were compared. From March 1995 to December 1998 we prepared twelve allografts using Cell Pro system for eight children with high-risk hematological malignancies and six autografts for six patients with severe autoimmune diseases. From January 1999 to October 2000 we prepared fifteen allografts using CliniMACS system for ten children with high-risk hematological diseases and inborn metabolic disorders or primary immunodeficiences, five allografts for three adult patients with high-risk hematological malignancies and two autografts for two patients with autoimmune diseases. In allogeneic transplantation the median purity of CD34+ cells in the final products after CellPro and E-rosetting was 85.6% (55.3%-95.7%); median recovery was 24.8% (17%-35%), median transplanted doses of T cells per kilogram of body weight were 0.66x10(4) (0-2.8); in autologous transplantation the median purity of CD34+ was 92.6% (55.6%-96%), median recovery was 28% (22%-46.2%), median transplanted doses of T cells per kilogram of body weight were 0.39x10(4) (0.0-3.6). After CliniMACS technique the median purity of CD34+ cells was 94.87% (69.15%-99%),medianrecoverywas 58% (30%-79.6%), median transplanted doses of T cells per kg of body weight were 0.254x10(4) (0-14.15); in autologous transplantation the median purity of CD34+ was 94% (94%-94%, median recovery was 97.4% (95%-99.8%), median transplanted doses of T cells per kilogram of body weight were 0.87x10(4) (0.49-1.24). We consider both methods of CD34+ selection and T cell depletion suitable for peripheral blood stem cell processing before mismatched hemopoietic stem cell transplantation in patients without identical donor or before autologous transplantation for severe autoimmune diseases. However, magnetic separation using CliniMACS system results in higher levels of purity and recovery with efficient T cell depletion.

Antigens, CD34↗
PubMed2000

Detailed monitoring of hematopoietic chimerism in a child treated by adoptive immunotherapy for high risk of relapse after BMT for acute myeloid leukemia.

We report a case of a 13-year-old boy who was transplanted for relapse of acute myeloid leukemia (AML). A detailed study of hematopoietic chimerism was performed using polymerase chain reaction (PCR) of variable number of tandem repeats (VNTR) at very short time intervals. We used discontinuation of post-transplant immunosuppression and donor lymphocyte infusions (DLI) in order to prevent leukemia relapse that was indicated by a progressive increase in autologous hematopoiesis. Despite the fact that the boy relapsed 10 months after BMT, we could see a significant influence of adoptive immunotherapy on the mixed chimerism status during the post-transplant period.

Acute Disease↗
PubMed1999

Use of a skin explant model for predicting GVHD in HLA-matched bone marrow transplants - effect of GVHD prophylaxis.

Over the last decade we have successfully evaluated the use of a human skin explant assay for predicting acute GVHD in HLA-matched sibling transplants. In the present study, we modified GVHD prophylaxis on an individual patient basis depending on the GVHD outcome predicted by the skin explant model. We have summarised our previous data describing how the skin explant assay results correctly predict GVHD occurrence and severity in 45/56 patients (80%); P< 0.0001, chi2 19.97, df = 1. In a further cohort of 19 patients, all were predicted to develop grade II or above GVHD. These patients were given increased GVHD prophylaxis with the addition of methotrexate and a significant reduction in the expected incidence of GVHD was observed (P = 0.02; chi2 7.7, df = 1; Fisher exact test P = 0.04). The results from these studies suggest that modifying GVHD prophylaxis, based on skin explant assay results, may reduce the expected incidence and severity of GVHD. We suggest that the technique might be used for selective GVHD prophylaxis in T cell non-depleted HLA matched sibling transplants.

Adolescent↗
PubMed1999

[A testicular tumor with features of a sex cord tumor with annular tubules and calcified large-cell Sertoli tumor].

An unusual testicular tumour with features of both sex cord tumour with annular tubules and large-cell calcifying Sertoli cell tumour is described. The tumour occurred in a 20-year-old man in the left testis as a 1 cm-measuring well circumscribed solitary lesion. Histologically, it showed sertoliform annular tubules with included eosinophilic nodules as well as isolated large cells and cords to sheets of the cells lying in a sclerosing stroma. A few psammomatous microcalcifications were seen. In contrast to similar cases reported before, the patient did not have any signs of Peutz-Jeghers syndrome, feminization or other complex dysplastic syndromes. The case indicates that tumours of this type may occur in phenotypically normal patients like pure large cell calcifying Sertoli cell tumours or ovarian sex-cord tumours with annular tubules. It further supports a close histogenetic relationship between these two entities.

Adult↗
PubMed1998

[Allogenic transplantation of hematopoietic stem cells in the treatment of children with high-risk acute leukemia].

BACKGROUND: Most children with acute lymphoblastic leukemia (ALL) and increasing number of children with acute myelogenous leukemia (AML) are currently cured with conventional chemotherapy. Despite of this success there is a subset of patients with high-risk features at diagnosis who are predisposed to a very high risk of relapse. Relapse of AML and early bone marrow relapse of ALL can not be cured by conventional chemotherapy. Allogeneic hematopoietic stem cell transplantation (HSCT) is therapeutic option in these children with very high-risk acute leukemia. METHODS AND RESULTS: Between XI/1989-XII/1996 33 children with acute leukemia (ALL: 22, AML: 11) underwent an allogeneic HSCT from HLA identical related donors (HLA-identical sibling: 30, twin: 1, other HLA-identical relative: 2) at the 2nd Dept. of Pediatrics, University Hospital Motol. Median age of our group was 9 years (1.5-19 y.), boys (n = 23) clearly dominated over the girls (n = 10). The resource of stem cells was bone marrow in 31 children, bone marrow and peripheral blood progenitor cells (PBPC) and PBPC in one child respectively. Myeloablative conditioning regimen varied, consisting of total body irradiation and chemotherapy in 21 children and chemotherapy in 12 children. HSCT was performed in first complete remission of acute leukemia in 9 children (AML: 7, ALL: 2), in second remission in 14 children (AML: 2, ALL: 12), in third remission in 4 children (ALL: 4). Six children underwent HSCT in first partial remission (n = 1) and in second (n = 4) or third (n = 1) chemoresistant relapse. Seven (21%) children died due to post-transplant complications. Nine (28%) children suffered from clinically significant acute graft-versus-host reaction (GVH) and 15% (4/27) children who survived 100 days post-transplant suffered from chronic GVH disease. Relapse of leukemia was diagnosed in 39% (12/31) children. Fourteen (42%) children are alive and well in continuous remission with median follow-up 42 months. CONCLUSIONS: Allogeneic HSCT can cure children with very high-risk acute leukemia in the situations where conventional chemotherapy fails. Relapse of leukemia and GVH reaction are most important causes of post-transplant morbidity and mortality.

Adolescent↗
PubMed1998

[DNA polymorphism, allogenic bone marrow transplantation and peripheral cell chimerism].

BACKGROUND: Bone marrow transplantation or transplantation of peripheral stem cells is an effective treatment of a number of diseases. Its increasing success and expanding use in associated with the development of molecular diagnostic methods which enable to follow up the graft from its engraftment in a recipient and then during the whole posttransplantation period at the level extremely small numbers of cells. METHODS AND RESULTS: In peripheral blood of patients, genotypes of the following loci were examined by polymerase chain reaction (PCR): APOB, COL2A1, D17S20, D1S80, HVR/1G, SRY and AMXY. Technique of restriction analysis was used for loci DXYS20 and DXYS75. 1. The first signs of donor bone marrow activity were observed in 50% of patients already at the beginning of the second week after transplantation, while in the second half of patients increasing number of donor cells in peripheral blood was noticed in the second and third week. 2. Engraftment with full and permanent substitution of own bone marrow without presence of recipients cells in peripheral blood--complete chimerism--was achieved only in a part of patients (cca 50%). 3. Peripheral blood of other patients did not contain only donor cells but also recipients cells--mixed chimerism. With regard to its onset, the authors have divided mixed chimerism into early and late, taking into account that some patients can develop both types. In patients under study, early chimerism was found more frequently, which apparently resulted from a shorter period of observation of lately transplanted patients. 4. In cases of oncohaematologic patients, which allowed to study specifically the presence of a pathologic clone, the follow-up of chimerism enabled to distinguish between relapse of the original disease and "biologic" recovery--resurrection of original disease-free haematopoiesis. 5. Regression of mixed chimerism was supposed to be the result of treatment focused at the original disease (CML), in some patients, however, it was a spontaneous process. CONCLUSIONS: Follow-up of cellular chimerism in transplanted patients by means of molecular genetic methods provides substantial information about patient's shape which can be utilized it is necessary to decide on treatment procedures. For this reason it is desirable that examination of chimerism by molecular methods should form integral part of care of these patients.

Adolescent↗