Prognostic impact of DNMT3A mutations in patients with intermediate cytogenetic risk profile acute myeloid leukemia

OBJECTIVES

Recently, mutations in DNMT3A gene have been described in about 25% acute myeloid leukemia (AML) cases, preferentially in monocytic AML. They were found to predict worse overall survival (OS) of mutated patients.

PATIENTS AND METHODS

RT-PCR followed by direct sequencing was used to test the presence of DNMT3A mutations in 226 AML patients with an intermediate-risk (IR) cytogenetics.

RESULTS

Sixty-seven patients of 226 (29.6%) carried a mutation in the DNMT3A gene. Occurrence of DNMT3A mutations was associated with female sex (P = 0.027) and with the presence of FLT3/ITD (P = 0.003), but not with particular FAB subtypes. Patients with DNMT3A mutation had higher initial WBC counts than those without it (P = 0.064) only because of higher incidence of FLT3/ITD within these cases. There was no difference between mutated and wild-type groups in reaching complete remission (CR) (P = 0.380). OS was not affected by DNMT3A mutation (P = 0.251), but OS of patients who reached CR was longer in DNMT3A negative cases (P = 0.025). Patients with DNMT3A mutation had a higher relapse rate (P = 0.007). Patients carrying both the DNMT3A mutation and FLT3/ITD relapsed more often than either patients with single DNMT3A mutation (P = 0.044) or patients with FLT3/ITD only (P = 0.058). DNMT3A mutations were associated with higher relapse rate even within the FLT3/ITD-negative group (P = 0.072). After reaching CR, these two genetic factors were independent predictors of relapse at multivariate analysis (P < 0.001). Only three of 30 'double-mutated' (FLT3/ITD+, DNMT3A+) patients are still alive, all of them having undergone hematopoietic stem cell transplant.

CONCLUSIONS

We have confirmed the high incidence of DNMT3A mutations in patients with AML with IR cytogenetics. Patients with DNMT3A mutations relapse more often and have inferior OS when only patients achieving CR are analyzed. 'Double-mutated' patients have a very poor prognosis.

[Prevalence of glycoprotein B (gB) genotypes in the patients with high risk of symptomatic cytomegalovirus infection]

OBJECTIVES

Based on genetic variability of the dominant envelope glycoprotein (gB), human cytomegalovirus is classified into four major genotypes. The aims were to determine the prevalence of particular gB genotypes in Czech CMV-infected patients and to compare three groups of the patients with high risk of symptomatic CMV infection, i.e., haematopoietic stem cell transplant (HSCT) recipients, HIV-positive persons and infants.

MATERIAL AND METHODS

The study was performed on 134 archived CMV-positive DNA isolates from the patients tested in the National Reference Laboratory for Herpesviruses in 2004-2007. For genotyping, the variable part of gB was amplified and analysed using the restriction fragment length polymorphism (RFLP) method.

RESULTS

The most frequently detected genotype was gB1 (33%), followed by gB2 (29%), gB3 (18%) and gB4 (7%). However, the distribution of gB genotypes varied between groups of high-risk patients: gB2 dominated in HIV-positives (55%, p = 0.004), while gB3 was most common in HSCT recipients (26%, p = 0.03) and gB4 was relatively more frequent in infants (20%, p = 0.03). In HSCT recipients, we found increased frequency of gB3 (26%, p = 0.03) and co-infection with two or more gB genotypes (17%, p = 0.016).

CONCLUSIONS

The distribution of CMV gB genotypes from Czech CMV-infected patients is similar to that reported in other European countries or in the United States. Differences in the prevalence of CMV gB genotypes between groups of high-risk patients indicate variation in biological properties of particular gB genotypes, possibly resulting in distinct virulence, immunogenicity or epidemiological characteristics of circulating strains.

Extracorporeal photochemotherapy (ECP) in treatment of patients with c-GVHD and CTCL

We evaluated the immunomodulatory and clinical effect of 279 extracorporeal photochemotherapy (ECP) procedures which were performed in six patients with chronic extensive GVHD and in two patients with CTCL (cutaneous T-cell lymphoma)/Mycosis fungoides. ECP was performed using the off line regimen. In five of six patients with c-GVHD the improvement of sclerodermatous skin changes, joint mobility, and the reduction of joint pain was observed. Two patients with CTCL responded to ECP with rapid improvement of the skin changes. In patients with c-GVHD and CTCL who responded to ECP efficiently, we found the similar tendency to increase in the number of CD 3/8+ T-lymphocytes and the decrease of CD 4/8 IRI. In patients with CTCL we observed also the decrease in levels of CD 3/4+ T-lymphocytes and in the number of leukocytes. The influence of ECP on T-cell subsets and on the dendritic cells function, which we observed in our previous study, leads to the suggestion that interactions between T-cell subsets and dendritic cells may participate in the process of ECP. ECP did not cause any significant changes in levels of IgG, parameters of liver and renal functions in patients with c-GVHD and with CTCL. No increased incidence of infections and no serious adverse reactions in patients have been observed so far.

[Allogeneic hematopoietic stem cell transplantation in patients with chronic myeloid leukemia in the Czech Republic--a retrospective analysis of results in years 1988-2005]

Analyses of hematopoietic stem cell transplantation (SCT) results are of high importance for decision-making on treatment strategy for patients with SCT as a possible therapeutic alternative. In this paper the Czech National Registry of SCT and Transplantation Centre in Pilsen present their joint retrospective analysis of the results of allogeneic SCT in patients with chronic myeloid leukemia (CML) performed in the Czech Republic from 1988 to spring 2005. 295 patients (179 men and 116 women) ranging in age from 6.9 to 59.5 years (median 37.3) underwent transplants. In most cases the donor was an HLA-identical sibling (164; 55.6%) or a voluntary unrelated donor from the register (110; 37.3%), in a minority of cases another relative of the patient (21; 7.1%). Myeloablative conditioning was used in 90% of patients. The source of hematopoietic stem cells was bone marrow in 57%, peripheral blood in 41% and combination of both in 2% of cases. 83.4% of patients underwent transplant in the chronic phase of the illness while 7.8% in the acceleration phase and 6.1% in the blastic phase respectively. The median interval from the diagnosis to SCT was 316 days. Median follow-up after SCT was 2 years. SCT was complicated by acute graft versus host disease of grade II-IV in 33.7% of patients and by chronic graft versus host disease in 36.3% of patients. Median survival was not reached, 18 (6.1%) of patients died due to the relapse of CML and the cause of 101 (34.2%) deaths was transplant-related. Significant trends were observed during the study period: SCT were performed more frequently in older patients, less than one year from the diagnosis, reduced-intensity conditioning was used more often and the source of hematopoietic stem cells was peripheral blood in the majority of patients (p = 0.188 - < 0.0001). Also, transplantation activity changed - the annual rate of SCT increased steadily until 1999, while there was no such an increase between 2000 and 2005. The use of peripheral stem cells was associated with chronic graft versus host disease (p = 0.007). In Cox multivariate analysis the EBMT risk score and the interval from the diagnosis to SCT were identified as independent factors in patient survival. An "ideal" patient, aged under 30, undergoing transplant in the chronic phase of CML within one year since the diagnosis after 2000 had a survival probability of 88% for three years after SCT. It can be concluded that results of allogeneic SCT in CML in the Czech Republic reflect current global trends, are comparable with results achieved in other countries and show significant improvements.

Prognostic relevance of the FAB morphological criteria in chronic lymphocytic leukemia: correlations with IgVH gene mutational status and other prognostic markers

Morphological examination is the routine first step in the diagnosis of hematological malignancies, including chronic lymphocytic leukemia (CLL). Atypical cell morphology according to the FAB criteria is known to herald disease progression. Several years ago, it was proposed that FAB morphology at diagnosis had a considerable prognostic impact. However, this proposal has not been widely adopted in practice. Thus we questioned the prognostic value of the morphological examination, which was performed retrospectively in 88 patients out of our 110 institutional registry patients (70 males and 40 females, median age 57 yrs) with CLL at diagnosis. We related the results to the more modern prognostic markers. Atypical FAB morphology was shown to correlate with IgVH gene mutation status, trisomy of chromosome 12 and deletion of 17p detected either by conventional G-banding or by fluorescence in situ hybridization (FISH) analysis. The correlation of FAB morphology with CD38 antigen expression or with the histopathological pattern of bone marrow infiltration was not significant. Overall survival (OS) data were available for 84 morphologically examined patients. The patients with atypical morphology (64 patients) had a significantly shorter OS (103 months) than the 20 patients presenting with typical CLL morphology (237 months; p=0.03). Only the mutation status of IgVH genes correlated more closely with OS (p=0.002). Of note, there was no leukemia-related death within "unmutated" cases who had typical FAB morphology (p=0.14), and vice versa, the mutation status had a significant prognostic impact within the morphologically atypical cases (p=0.01). Thus FAB morphology and the mutation status may yield complementary prognostic information. OS was affected both by the presence of cytogenetic aberrations (p=0.03) - most adversely by deletions of 17p and 11q, and by CD38 expression (p=0.003). We conclude that careful examination of peripheral blood smears according to FAB is a simple, cheap and valuable tool in the first-line assessment of prognosis of CLL patients and should not be overlooked even in 3rd millennium when more sophisticated prognostic markers are at hand. This ought to be confirmed in larger prospective studies with multivariate analysis of data.

Combined stratification of refractory anemia according to both WHO and IPSS criteria has a prognostic impact and improves identification of patients who may benefit from stem cell transplantation

A retrospective analysis of the relationship between the initial classification according to either FAB or WHO criteria, the presence of risk factors and the type of therapy including stem cell transplantation (SCT) on the survival was performed in a group of 106 patients with primary myelodysplastic syndrome (MDS) of FAB RA subtype. Allogeneic SCT early in the course of the disease did not significantly affect median survival in RA patients evaluated either according to FAB criteria (63.2 months in 17 SCT patients versus 64.4 months in 89 non-transplanted (non-SCT) patients) or in subgroups classified separately according to WHO (64.0 months in SCT versus 91.0 months in non-SCT RA patients and 66.2 months in SCT versus 43.0 months in non-SCT refractory cytopenia with multilineage dysplasia (RCMD) patients) or International Prognostic Scoring System (IPSS) criteria despite decreased incidence of leukemic transformation (5% in SCT versus 32% in non-SCT patients). Neither univariate or multivariate analysis of different clinical and laboratory parameters revealed a significant effect of SCT on 3 or 5 years survival in RA patients. The most probable explanation was a relatively high rate of transplantation related mortality (41%) on one hand together with a slow disease progression towards leukemia (24% at 5 years in non-SCT) on the other hand. A more refined stratification of patients based on the combined WHO morphology classification and IPSS cytogenetic criteria revealed subgroup of 11 non-SCT patients with RCMD and poor karyotype with median survival significantly different from that in five SCT patients (9.2 months in non-SCT versus 89.3 months in SCT, P=0.05). Thus, combined WHO morphology/IPSS cytogenetics criteria may be helpful for identification of the high risk patients with the RA group who may benefit from early SCT despite the relatively high incidence of SCT-related complications.

Molecular monitoring of responses to DLI and DLI + IFN treatment of post-SCT relapses in patients with CML

We monitored DLI treatment of 13 post-SCT relapses using quantitative competitive (QC) RT-PCR for BCR-ABL (sensitivity 10(-5)) and compared responses to DLI alone and DLI in combination with interferon-alpha (IFN). Ten relapses (one blast crisis, five cytogenetic and four molecular) were treated with DLI+IFN, three relapses (one cytogenetic, two molecular) were treated with DLI alone. Except the patient treated in blast crisis, who died, all the patients treated with DLI+IFN achieved complete molecular remission, with the median time interval of 3.9 months (range 0.25-10.5 months). None of the three patients treated with DLI alone have achieved complete molecular remission up to now, i.e. 32, 45, and 50 months after DLI. However, in all of them some decrease of BCR-ABL transcript level was detected. Although the retrospective analyses did not confirm that IFN improved the response to DLI, our results based on sensitive molecular monitoring suggest that DLI effect, at least in some patients, is supported by IFN administration.

[Long-term results of the UHKT-911 study of adult patients under 65 years of age with de novo acute myeloid leukemias without favorable karyotypes]

Between February 1991 and April 1994 induction chemotherapy of 32 adult consecutive patients under 65 years with de novo acute myeloid leukemias (AML) was started in the study UHKT-911. They were 19 women and 13 men, aged 18-63 (median 44) years. Their AML were classified according to the FAB classification: 3 M0, 3 M1, 9 M2, 14 M4, 3 M5. Induction chemotherapy consisted of 1-2 cycles with 3-4 doses of daunorubicin (DNR) 45 mg/m2/d i.v. and 14 doses of cytosine arabinoside (Ara-C) 200 mg/m2 per 3-h infusion every 12 hours. After the treatment patients, not being in complete remission, got the HD cycle with 10 high-doses of Ara-C 2000 mg/m2 per 3-h infusion every 12 hours i.v. and DNR 45 mg/m2/d i.v. on days 4 and 5, then the EMi cycle composed of etoposide 100 mg/m2/d i.v. for 5 days and mitozantrone 10-12 mg/m2/d i.v. on days 1, 3 and 5. Complete remission (CR) was achieved in 25 of 32 (78%) patients after 1-3 cycles. Five patients died between days 5 and 24 of treatment of infections, two patients were resistant to 4 cycles of induction therapy and survived 8.4 and 13.5 months. Three patients chose allogeneic bone marrow transplantation in their 1st CR from their relatives. Two of them have been living in CR for 115 a 110 months since diagnosis, the third died of sepsis on the day 52 after transplantation. Two patients in CR died of infections after their 2nd. consolidation cycle. Twenty patients in CR completed 2-4 consolidation cycles (1-3 HD, 1 EMi). Median of their CR duration was 17.8 (2-117) months. Relapse appeared in 12 cases after 4.4-34.8 (median 12.5) months, 8 patients (6 women and 2 men, aged 29-63 years) have remained longer than 5 years in their 1st. CR. Cytogenetic examination of their bone marrow showed a normal karyotype in 4 cases, 1x 46,XX,del(1)(p32p34), 1x 46,XX,16p+, 1x 47,XX,+mar, 1x 46,XX,del(5)(q22q33). After 62 months in CR a pancytopenia with dysplastic bone marrow changes developed in one of them, probably a secondary myelodysplastic syndrome, lasting for further 33 months. Event-free survival at 5 years was 27.5% (8/29 patients), significantly better (p = 0.046) against 7.5% (3/40) patients treated without HD cycles in the years 1982-1987. The same difference was observed in 7.5-year overall survival (p = 0.036) between the two studies, when 3 of 6 patients 60-64 years old remain in their 1. CR.

[Allogenic bone marrow transplantation]

Allogeneic bone marrow transplantation (alloBMT) represents an important part of the therapeutic approaches in many malignant as well as non-malignant hematological diseases. For some of them it represents the only curative strategy available, in others it may improve the outcome of treatment in high-risk stages. Curative potential of alloBMT consists of the curative potential of cytostatic activity of the pre-transplantation treatment and of so-called graft versus leukaemia effect (GVL), which is mediated by transplanted lymphocytes. GVL seems to be one of the most effective mechanisms in the treatment of many hematological malignancies and it is therefore studied in the context of the nonmyeloablative transplantations (minitransplantations).

[Myelodysplastic syndrome--classification, prognosis and therapy]

BACKGROUND

The impact of classification, prognostic factors and treatment on survival and rate of leukemic transformation was analysed in 197 patients with primary myelodysplastic syndrome (MDS) treated in the Institute of Hematology and Blood Transfusion in the years 1980-2000.

METHODS AND RESULTS

The patients were classified according to the FAB criteria and divided into risk groups according to the International Prognostic Scoring System (IPSS). A separate evaluation of 34 patients who underwent stem cell transplantation and of 163 of those not transplanted was performed. Median survival of not transplanted patients with RAEB (10.0 months) and RAEB-T (12.0 months) was significantly shorter than survival of RA (62.4 months) and RARS (48.1 months, P < 0.001) patients as well as survival of patients included in intermediate II. (13.8 months) and high (10.8 months) risk subgroups when compared to those with low (74.9 months) and intermediate I. risk (56.0 months, P < 0.001). A similar difference was observed in percentage of patients evolving towards acute leukemia and in estimated 3 years survival (EFS). EFS of RA patients was 57% in contrast to 4% in RAEB-T group (P < 0.001) in the same way, EFS in low risk subgroup was 79% vs. 3% in high risk patients (P < 0.001). Chemotherapy alone did not significantly affect median survival of patients with advanced MDS when compared with supportive care. On the contrary, median survival of transplanted patients with RAEB and RAEB-T was 38.4 months in comparison to 11.5 months in those not transplanted (P < 0.001) and 36.8 months vs. 12.0 months in transplanted and not transplanted patients with intermediate II. and high risk (P = 0.05). The difference in survival between transplanted and not transplanted patients with RA and in patients in low and intermediate I. risk subgroups was not statistically significant.

CONCLUSIONS

We confirmed an adverse effect of excess of blasts on prognosis of patients with primary MDS. Stem cell transplantation had a significant beneficial effect on survival of patients with RAEB or RAEB-T as well as of patients included in intermediate II. or high risk subgroups. The impact of stem cell transplantation on survival of patients with RA or with low or intermediate I. risk was not significant. Therefore, further criteria should be taken in account for indication of stem cell transplantation in these subgroups of patients.

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).

The relationship between HA-1 compatibility and the activation of helper T lymphocyte precursors

The relationship between the compatibility in minor histocompatibility HA-1 antigen and the activation of helper (IL-2 producing) T lymphocyte precursors in vitro was studied in the group of 17 HLA-A2 positive HLA identical siblings. Although the number of pairs studied is still small, no correlation has been found between HA-1 compatibility and helper T lymphocyte precursors activation. The results presented here could suggest the possibility that the HTLp assay does not have to be a relevant parameter for the detection of HA-1 mismatches in HLA identical siblings.

[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.

Presence of herpes simplex virus (HSV) in peripheral leukocytes of patient who developed active HSV infection after bone marrow transplantation

BACKGROUND

Despite of prophylactic antiviral therapy, latent HSV may be reactivated in bone marrow transplant (BMT) recipients and cause serious disease. Rapid diagnosis of HSV infection is needed to prompt institution of appropriate therapy.

OBJECTIVES

We report a case of the allogenic BMT recipient, who developed ulcerative esophagitis which progressed to generalized HSV infection and graft versus host reaction (GVHR).We consider several diagnostic approaches to detection of active HSV infection in this patient.

STUDY DESIGN

Polymerase chain reaction (PCR) was used to detect HSV DNA in esophageal biopsy specimens and peripheral leukocytes (PBL). Isolation of HSV in tissue culture was performed to prove infectious virus in swabs from mucocutaneous lesions or in PBL.

RESULTS

Using PCR, HSV DNA was detected in peripheral leukocytes of the patient who had developed generalized HSV infection accompanied with hepatosplenomegaly and hepatitis. At that time, a fully infectious ACV-resistant HSV was isolated from his PBL. On the other hand, HSV DNA was not detected in PBL of other BMT-recipients with skin- or organ-localized infection.

CONCLUSIONS

Presence of HSV-DNA in PBL of BMT recipients can signalize generalized HSV infection. Isolation of HSV from PBL by cocultivation with human fibroblasts can be used as an alternative diagnostic approach in these patients.

[Stem cell transplantation for paroxysmal nocturnal hemoglobinuria]

Paroxysmal nocturnal hemoglobinuria (PNH) represents a rare clonal disorder of hematopoiesis clinically characterized by acquired hemolytic anemia, intravascular hemolysis, hemoglobinuria and frequent occurrence of venous thrombosis. Stem cell transplantation is indicated in patients with severe bone marrow aplasia, repeated massive hemolysis or recurrent life threatening thrombotic complications. Almost 90 transplanted patients with PNH have been published. We report a case of successful allogeneic peripheral blood stem cell transplantation performed in a 24 years old woman with a severe form of PNH with frequent episodes of massive intravascular hemolysis. The patient is now alive completely engrafted 900 days after transplantation without signs of chronic GVHD and without recurrent infections. This case represents the first successfully transplanted patient with PNH in our country.

Prediction and reversion of post-transplant relapse in patients with chronic myeloid leukemia using mixed chimerism and residual disease detection and adoptive immunotherapy

In the prospective study, we examined hematopoietic mixed chimerism (using polymerase chain reaction (PCR) of variable number of tandem repeat-VNTR sequences) and minimal residual disease (MRD) status (using qualitative and in the case of positivity quantitative reverse transcriptase polymerase chain reaction (RT-PCR) for the BCR/ABL fusion mRNA) in serial peripheral blood samples taken from 25 patients after bone marrow transplantation (BMT) for chronic myeloid leukemia (CML). Increasing mixed chimerism in correlation with increasing signal of MRD was detected in 10 patients. In two patients mixed chimera status and BCR/ABL rearrangement led to hematologic relapse, in five patients molecular relapse was followed by reappearance of Ph chromosome and three patients developed molecular relapse only. Adoptive immunotherapy-donor lymphocyte infusion (DLI), interferon (INF) and discontinuation of post-transplant immunosupression-separately or in different combinations was used in nine patients with molecular, cytogenetic or hematologic relapse of CML. The results demonstrate that significant response at the molecular level can be achieved for a majority of CML patients and that using of all forms of adoptive immunotherapy controlled by MC and MRD is more efficient in patients treated in early molecular relapse-with minimal disease burdens.

Predictive value of HLA class II PCR typing for the outcome of mixed lymphocyte reaction

The use of HLA-DRB1 and -DQB1 polymerase chain reaction-sequence-specific primer (PCR-SSP) typing at different levels of resolution for MLR prediction was assessed in 54 HLA-A and -B matched donor/recipient unrelated pairs and 89 HLA-A and -B identical siblings. Graft-versus-host (GvH) direction one-way MLR was evaluated unless stated otherwise. The typing of DRB1 alleles satisfactory for MLR prediction in HLA identical siblings (P = 0.0015) does not appear to be sufficient in matched unrelated pairs (P = 0.2407). Using more discriminatory PCR-SSP typing, the disparity in DRB1 allelic subtypes was predominantly found in the category of DRB1 allele compatible, MLR positive unrelated pairs. Besides, DRB1 allelic subtype mismatches were revealed in five of the forty-one DRB1 allele compatible, MLR negative unrelated pairs. More discriminatory typing made the correlation between DRB1 compatibility and MLR negativity extremely significant (P = 0.0001). As for these five exceptional cases, the reciprocal host-versus-graft (HvG) direction MLR was considered, too. This allowed HLA-D disparity to be disclosed in two of them. An uninterpretable result reflecting defective MLR reactivity occurred in one case. Negative reciprocal MLR in the last two DRB1 allelic subtype incompatible pairs is hardly to explain without postulation of MLR silent DRB1 allelic subtype mismatches. An analysis in unrelated pairs showed a role of some DQB1 gene products in the proliferative response too. GvH direction positive MLR was found in two HLA identical siblings among the 89 tested. The DPB1 incompatibility detected in one of them could be a potential cause of proliferative response but MLR reactivity in the other, DPB1 identical, pair cannot be interpreted easily.

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.

Transplantation of allogeneic peripheral blood progenitor cells--a single centre experience

13 patients have been transplanted at Institute of Hematology and Blood Transfusion since 1995 using allogeneic PBPC either alone or with bone marrow as a source of progenitor cells. All donors were G-CSF mobilised HLA identical family members. PBPC harvests were performed on D 4,5, (6) of G-CSF administration. The medium content of TNC, CD34+, CD3+, CD4+and CD8+cells/kg b.w. of the recipients in the grafts were: 13,1x10(8)(TNC), 11,4x10(6)(CD34+), 393x10(6)(CD3+) 243x10(6)(CD4+), 125x10(6)(CD8+) The patients received either BuCy2 or CyTBI preparative regimen and Cyclosporin A + short course of Methotrexate for GVHD prophylaxis. Engraftment of ANC >500 was achieved by D+16 and PLT >20.000 by D+19. Three of ten evaluable patients developed acute and three of nine chronic GVHD. 8 patients survive with the longest follow up 776 days.

An overview of the Czech Bone Marrow Donor Registry

The Czech Bone Marrow Donor registry (CBMD) was founded in 1991 in the National HLA centre at Prague's Institute for Clinical and Experimental Medicine. In the same year, the CBMD submitted its data to the Bone Marrow Donors Worldwide (BMDW). Another line of CBMD's international cooperation is accomplished through computer linkup with the European Donor Secretariat (E.D.S) network. Donors are being recruited constantly through blood transfusion units and other volunteers are enrolled through the mass media. All the methodology used is developed in compliance with the standards of the European Federation for Immunogenetics (EFI). CBMD closely cooperates with clinical centres for transplantation of bone marrow, stem cells (PBSC) and cord blood from unrelated donors. More than 7,000 potential bone marrow typed in HLA-A, B locus have been registered. Besides potential bone marrow donors, frozen cells of cord blood are kept by CBMD. Search requests from registries all over word come via E.D.S. daily except for weekends. Since its foundation in 1991, nearly 20,000 international requests have been handled. During the last two years, 5 CBMD donors provided their bone marrow to Czech patients, one donor provided stem cells (PBSC) and one donor provided bone marrow + stem cells (PBSC). To date, more than 20 transplantations from unrelated donors have been performed in Prague's transplant centres.

[Interferon alpha--the drug of choice for patients with chronic myeloid leukemia]

BACKGROUND

The conventional, or standard, treatment of chronic myeloid leukaemia (CML) with hydroxyurea and busulfan has no marked influence on its course or duration. Interferon (IFN) alpha administration has, on the other hand, been shown to induce not only a haematological but also cytogenetic response, i.e. partial or complete bone marrow repopulation by Ph-negative cells. This has triggered studies comparing IFN and conventional chemotherapy. The present work had the purpose to gain experience with IFN alpha treatment and compare the results with hydroxyurea and busulfan treatment, in the chronic phase of CML.

METHODS AND RESULTS

Therapeutic results obtained in 30 patients given IFN alpha and 30 others given conventional chemotherapy were evaluated retrospectively. In spite of the short time of IFN administration (4-27 months), significantly more complete haematological responses (83%) were observed in this than the conventional chemotherapy group (57%). Cytogenetic responses were achieved in 36%, complete cytogenetic remission in 20% of IFN-treated patients. Conventional chemotherapy produced no cytogenetic effect.

CONCLUSION

The results obtained confirm the value and efficacy of IFN-alpha treatment in CML patients, especially if it is started early and the dose is effective. Regular cytogenetic monitoring is necessary. Longer follow-up of the patients will be necessary for evaluation of the IFN effect on the length of their survival.

Helper T lymphocyte precursor frequency analysis in alloreactivity detection

The utility of IL-2 secreting helper T lymphocyte precursors (HTLp) frequency testing has been evaluated for detecting alloreactivity. The frequency of HTLp was approached by limiting dilution assay. High HTLp frequency was detected in 20 out of 30 HLA matched unrelated pairs (67%). The comparison of HTLp and CTLp (cytotoxic T lymphocyte precursors) frequencies in HLA matched unrelated pairs showed that the two examinations are not fully alternative in detecting alloreactivity. This could suggest the utility of combined testing of both HTLp and CTLp frequencies for alloreactivity assessment. In contrast, five positive HTLp values were only found among 28 HLA genotypic identical siblings (18%). Previous CTLp limiting dilution studies showed very low or undetectable CTLp frequency results in that group. For that, HTLp assay remains to be the only cellular in vitro technique detecting alloreactivity in these combinations.

[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.

[Analysis of HLA class I molecules using isoelectric focusing. Its application in selection of bone marrow donors]

BACKGROUND

Differences between HLA proteins class I are assessed by serological typing using HLA allo-antisera. This method suffices for the assessment of HLA signs in allogenic transplantations of bone marrow in genotypically identical siblings. However, it does not suffice in the selection of donors from the wider family of a related or not related donor from the register of voluntary bone marrow donors. In order to assess the polymorphism of the HLA-class I not detected by serological typing other more sensitive techniques are introduced. In the authors department one-dimensional isoelectric focusing was introduced as an auxiliary method for evaluation of identity of molecules in HLA-class I between bone marrow recipient and donor.

METHOD AND RESULTS

The authors introduced the method of one-dimensional isoelectric focusing which uses for detection of molecules of HLA-class I a polyclonal antibody against heavy chains of HLA molecules class I and a secondary antibody labelled by alkaline phosphatase. Forty-one pairs of bone marrow donors and recipient were examined. In six instances, i.e. in almost 15%, the authors detected by isoelectric focusing disagreement in HLA molecules class I. The authors present three interesting pairs of donors and recipients where isoelectric focusing helped with the selection of a suitable bone marrow donor.

CONCLUSIONS

The isoelectric focusing is at present another method which helps to reveal differences in HLA class I molecules. When methods of DNA analysis are introduced to recognize alleles of the HLA-I class, correlation with serologically and biochemically assessed variants wil be an essential guide in the evaluation of the final typing of HLA molecules class I.

[Frequency of cytotoxic and helper T-lymphocyte precursors in donors with alloreactivity to recipient histocompatibility antigens. Possible use in predicting acute graft vs host disease in bone marrow transplantation]

BACKGROUND

The utility of cytotoxic T lymphocyte precursor (CTLp) and helper T lymphocyte precursor (HTLp) frequencies estimation for detecting alloreactivity and for the prediction of acute graft versus host disease (aGVHD) has been evaluated.

METHODS AND RESULTS

The limiting dilution assay and a maximum likelihood statistical programme were used for CTLp and HTLp frequency estimation. A high CTLp frequency suggesting the presence of hidden class I mismatches was detected in 41.2% of unrelated pairs. HLA-A and -B matched by serological typing and DRB1 and DQB1 matched by DNA analysis. Severe aGVHD (grade III-IV) occurred in all patients of this group who underwent bone marrow transplantation (BMT). In two patients of the three evaluated with low pretransplant CTLp frequency a mild form (grade I) or no aGVHD developed after unrelated BMT. Positive frequency of alloreactive HTLp was found in 50% of HLA matched unrelated pairs. The comparison of CTLp and HTLp values in the same individuals showed that these two methods are not fully alternative in detecting alloreactivity. In the group of HLA identical siblings, 18.7% of positive HTLp results were only found. Besides HLA-DP incompatibilities, the differences in non-HLA genes could cause this alloreactivity.

CONCLUSIONS

CTLp assay has a potential for the prediction for aGVHD development following BMT from HLA matched unrelated donors. CTLp results suggest the necessity of more accurate class I typing in these cases. The comparison of CTLp and HTLp frequencies showed that the results can differ in some unrelated donor-recipient BMT pairs suggesting the convenience of simultaneous performing of both assays for the alloreactivity assessment. More cases have to be considered to determine the relationship between pretransplant HTLp frequency and posttransplant aGVHD development in HLA identical siblings.

[Donor selection for allogenic bone marrow transplantation from 1991 to 1995. (The Prague Center for Bone Marrow Transplantation)]

BACKGROUND

The prerequisite of successful transplantation of haematopoietic stem cells is to find a suitable, i.e. HLA matched bone marrow donor. In the submitted paper the authors give an account of the strategy of selection of bone marrow donors, as practised by the Prague transplantation group.

METHODS AND RESULTS

In 1991 to 1995 (end of first quarter) the authors sought suitable bone marrow donors for 421 patients where an allogenic bone marrow transplantation was indicated. During that period 95 transplantations were performed (22.5% of all indicated cases), incl. 82 from siblings (86.3%) of the implemented allogenic bone marrow transplantations). A HLA matched donor from the wider family circle was selected for 15 donors, transplantation were performed in 6 patients (6.4% of the implemented allogenic bone marrow transplantations). An unrelated bone marrow donor was sought for 41 patients as no donor was found in the wider family. Transplantation was implemented in 7 of these patients (7.3% of the implemented transplantations.

CONCLUSIONS

With the increasing experience of our transplantation centre, no doubt, the ratio of other than sibling transplantations of bone marrow will increase. At present it accounts for 13.7%. The task of our HLA group must be selection of donors matched as well as possible with the recipient according to all available tests of tissue compatibility - from the wider family circle as well as from the register of unrelated donors.

[Treatment of chronic myeloid leukemia with bone marrow transplantation at the Institute of Hematology and Blood Transfusion in Prague]

The outcomes of bone marrow transplantation (BMT) performed at the Institute of Haematology and Blood Transfusion from April 1988 to December 1994 in 31 patients with chronic myelogenous leukemia are presented. Age of the patients range from 18 to 49 years, median 34 years. Male:female ratio was 1.58:1. The conditioning regimen consisted of Cyclophosphamide and total body irradiation (TBI) or Busulfan and Cyclophosphamide. The results are evaluated as of January 1, 1995. Nineteen patients (61.3%) are alive, 12 patients (38.7%) died. The causes of death are discussed. The median time of follow up all patients is 10.4 months, range 0.3-81.5. The median time of follow up of surviving patients is 21.8 months, range 2.5-81.5. Probability of 2 years survival by Kaplan-Meier analysis is 58 +/- 10%. Of the 24 transplanted in the first chronic phase, 18 patients are alive. Of the 7 transplanted in advanced phase of the disease, 1 patient is alive. Of the 27 patients, who received bone marrow from an HLA identical sibling, 19 are alive. Of the 4 patients who received bone marrow from other donor than an HLA identical sibling, none is alive. Acute GvHD III.-IV. grade developed in 5 patients (16.1%), moderate and severe chronic GvHD developed in 11 patients (31.5%). Cytogenetic relapse was diagnosed in 1 patient, hematological relapse in 2 patients. Karnofsky scores of patients surviving after BMT range from 30% to 100%, median 90%.

[Results of induction therapy in newly diagnosed acute myeloid leukemias in study 911 at the Institute of Hematology and Blood Transfusion]

Thirty-seven patients with de novo acute myeloid leukemias were admitted to the Institute of Hematology and Blood Transfusion in Prague in February 1991-December 1993. Their age was 18-85 years with a median of 46 years. Two patients died on the day of admission, chemotherapy was initiated in 35 patients. Altogether 27 patients (77%) achieved complete remission (CR), i.e. 18 (81%) of 22 patients younger than 55 years and 9 (70%) of 13 patients older than 55 years. Only 7 (35%) of 20 patients achieved CR after a single therapy course 3/7 consisting of 3 doses of daunorubicin 45 mg/m2 on days 1, 3, 5 and cytosine arabinoside 150-200 mg/m2 every 12 hours for 7 days. However, 8 (61%) of 13 patients achieved CR after a single treatment course 4/7 with 4 doses of daunorubicin 45 mg/m2 on days 1, 3, 5, 7 and identical doses of cytosine arabinoside as in the 3/7 treatment. We used the course with 10 high-doses of cytosine arabinoside 2000 mg/m2 every 12 hours and daunorubicin 45 mg/m2 on days 4 and 5 (treatment HDAC/DNR) as the 1st, 2nd or 3rd induction therapy in 12 patients and 9 (75%) of them achieved CR. The treatment was associated with a high toxicity. An intensified therapy 3/7h similar to the 3/7 one but with the doubled dose of cytosine arabinoside 300-400 mg/m2 on days 5-7 was given to 5 patients as the 2nd induction but it did not improve the CR rate and it was associated with a high toxicity similar to the HDAC/DNR therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

[Late and slow diagnosis of acute promyelocytic leukemias--the main cause of early death]

Acute hypergranular promyelocytic leukemia (AML M3) belongs to malignant diseases leading very rapidly to death. Immediate treatment based on early diagnosis may cure one third of patients. The typical finding in peripheral blood of patients is pancytopenia with or without atypical promyelocytes. In published studies only 15-25% patients exhibit leukocyte counts above 10 x 10(9)/l. Five of our ten patients studied had leukocyte count above 10 x 10(9)/l. The difference might be in connection with late and slow diagnosis of AML M3. AML is not taken into consideration during medical examination even if the disease occurs in medical family. Thus we describe clinical signs of AML M3 that could be divided into three main groups: bleeding, infections and anemia. In patients with bleeding or anemia or with infections repeating within a short period or with an infection and concurrent signs of bleeding or anemia the complete blood cell count should be examined immediately. If blood cell count abnormalities are found the patient should be sent immediately to hematology unit for further examination and treatment. Early diagnosis enables to start "differentiation therapy" with all-trans retinoic acid that could be administered as monotherapy only in patients with leukocytes below 5 x 10(9)/l. Early diagnosis of AML M3 might ameliorate the fate of patients, since four of our five patients referred to us with elevated leukocyte counts expired in the first five days.

[The effect of thrombocytapheresis on hematologic, biochemical and immunologic indicators]

The authors investigated in 33 separate donors the influence of thrombocytapheresis on haematological, biochemical and some immunological parameters. The paired t-test revealed a statistically significant increase of values of total proteins, aspartate aminotransferase, immunoglobulin A, alpha 1 antitrypsin, transferrin and the C4 component of complement seven days after apheresis and a significant increase of thrombocyte, total protein, alkaline phosphatase, immunoglobulin A, orosomucoid, and transferrin levels two weeks after apheresis. A significant decrease of haemoglobin values was recorded 7 and 14 days after apheresis. As the revealed changes of the investigated parameters are within the physiological range of the healthy adult population, the authors conclude that thrombocytapheresis does not have an adverse effect on the health status of donors.

[The significance of the thrombocyte crossmatching test]

The authors investigated the dependence of the results of the crossover test with thrombocytes and lymphocytes of the donor and serum of the recipient on the rise of thrombocytes 1 and 24 hours following administration of a thrombocyte concentrate. The clinical condition of the patient at the time of thrombocyte administration was taken into account. The donor of thrombocytes isolated in a blood element separator was selected from a panel of cca 800 subjects with previously assessed HLA antigens. A total of 36 administered concentrates was evaluated. From the assembled findings it may be concluded that the result of thromboconcentrate transfusion is significantly influenced by adverse clinical factors in the patient such as splenomegaly, haemorrhage, febrile conditions. A positive crossover lymphocytotoxic test can predict reliably the ineffectiveness of thrombocyte administration. A positive crossover test with the donor's thrombocytes does not affect significantly the success of the transfusion. It seems thus that for the fate of administered thrombocytes the presence of HLA antibodies is decisive and not the presence of specific thrombocytic antibodies.

[Therapeutic effectiveness of thrombocyte concentrates in relation to the results of the lymphocytotoxicity test]

The authors analyze the effect of transfusions of 211 thrombocyte concentrates to polytransfused patients in relation to the results of the crossover test between donor and recipient, using the lymphocytotoxic test (LCT). In negative LCT tests the adequate and inadequate effect was 50%. After elimination of non-immune influences (splenomegaly, febrile temperature) the percentage of adequate effects rose to 70%. In LCT positive results the effect of administration of thrombocyte concentrates declined to 30%. The authors discuss practical possibilities and ways to select suitable donors to achieve an optimal therapeutic effect of substitution therapy.

[Comparison of the Haemonetics V50, Fenwal CS 3000 and IBM 2997 blood separators]

Haemonetics V 50 (HV-50), Fenwal CS 3000 (FCS-3000) and IBM 2997 separators are compared according to the results of donor plateletaphereses. The mean platelet yield of HV-50, FCS-3000 and IBM-2997 was 464 X 10(9), 551 X 10(9) and 468 X 10(9) respectively (the difference both between FCS-3000 and HV-50 and between FCS-3000 and IBM-2997 being significant - p less than 0.01). The median leukocyte contamination of platelet concentrates was 0.3 X 10(9), 0.2 X 10(9) and 5.3 X 10(9) respectively (the difference between FCS-3000 and HV-50 being not significant). The separators are further compared on the basis of platelet concentrate volume, erythrocyte contamination of thromboconcentrates, processing time, donor and staff convenience, our experience concerning product reliability and service quality, and finally the price of both the separators and the disposables.

Effects of salt concentration and counterion on stability of alkali ion-18-crown-6 complexes in aqueous and methanolic solution: A conflicting evidence from potentiometric and sodium-23 NMR studies

Contrary to expectation, the title effects observed concurrently by potentiometry with ion-selective electrode and by sodium-23 NMR spectroscopy are completely different. The potentiometric stability constants for the sodium ion-18-crown-6 complex (KISE) exhibit a very pronounced variation with the counterion, KISENaSCN > KISENaCl > KISENaOH, as well as with the sodium salt concentration, the KISENaSCN/KISENaOH ratio being about 1.5, 2.0, 5.0 and 20 in the 0.01, 0.1, 0.5 and 1.0 mol l-1 aqueous and about 2.0, 12, 600 and 2 500 in the 0.01, 0.1, 0.5 and 1.0 mol l-1 methanolic solution, respectively. Whereas, the corresponding spectroscopic stability constants, KNMR, are virtually insensitive to the changes of counterion as well as to the salt concentration the overall spread of the KNMR values being less than 3. Resolution for the conflicting evidence is provided in terms of the activity coefficients γML+, γM+, γL differentiating between the concentration (Kconc) and thermodynamic (Kth) stability constants in the relation Kconc = (γM+ γL : γML+) Kth. At variance with the current opinion it is shown that only KISE are clean concentration constants subjected to the γML+/γM+ γL variation, while KNMR are hybrids between the concentration and thermodynamic constant leaning assumedly to the latter (Kth). Concerning the powerful effect of counterion and salt concentration of KISE, it is attributed to a large variation of γML+. No satisfactory explanation can be, however, offered in customary terms of the Debye-Hückel theory.

The arrangement of nucleotides in the coding regions of natural templates

The relation of the nucleotide sequences in the coding regions of natural templates and of the short nucleotide sequence in 3' terminus of 16 S ribosomal RNA was found to differ from random pattern. The observation is interpreted in terms of both the ribosomal interactions and the molecular evolution.

Base pairing mRNA-rRNA. The arrangement of nucleotides in the message for coat protein of phage MS 2

The relation of the nucleotide sequences in the message and of the short nucleotide sequence in 3' terminus of 16 S ribosomal RNA was found to differ from statistical expectancy. The observation is interpreted in terms of both the ribosomal interactions and the molecular evolution.

High resolution thermal denaturation of mammalian DNAs

High resolution melting profiles of different mammalian DNAs are presented. Melting curves of various mammalian DNAs were compared with respect to the degree of asymmetry, first moment, transition breath and Tmi of individual subtransitions. Quantitative comparison of the shape of all melting curves was made. Correlation between phylogenetical relations among mammals and shape of the melting profiles of their DNAs was demonstrated. The difference between multi-component heterogeneity of mammalian DNAs found by optical melting analysis and sedimentation in CsCl-netropsin density gradient is also discussed.