The Obesity Controversy: Does It Impact Treatment Response in Diffuse Large B-Cell Lymphoma?

Background: We aimed to investigate the association of body mass index (BMI) with treatment response in patients with DLBCL. Material and Methods: Seventy-nine DLBCL subjects were included in this study. Data about patient age, sex, serum LDH level, presence of B symptoms, IPI score, ECOG performance score, disease stage, extranodal involvement, and BMI values at diagnosis were retrieved by retrospective patient record review. Patients were staged according to Ann Arbor classification using CT and/or PET/CT findings, and the presence of B symptoms. Body mass index was calculated by dividing weight in kilograms by height in meters squared (kg/m2). Patients were divided into groups according to their BMI as underweight (BMI≤ 18.5 kg/m2), normal weight (BMI 18.5-25 kg/m2), overweight (BMI 25-30 kg/m2), and obese (BMI≥ 30 kg/m2), as defined by the World Health Organization. Results: Patients were divided into four groups according to their BMIs, but because there was only one patient in the underweight group, comparisons were performed between normal-weight, overweight, and obese patients. There was no statistically significant difference between these groups in terms of age, sex, serum LDH level, disease stage, presence of B symptoms, extranodal involvement, ECOG performance score, IPI score and treatment response (p= 0.070, 0.704, 0.325, 0.464, 0.254, 0.152, 0.658, 0.620, and 0.947, respectively). Conclusion: In our study, we showed that BMI has no significant impact on treatment response in patients with DLBCL.

Eltrombopag in the Treatment of Immune Thrombocytopenia: Two-Center Experience from Istanbul

Immune Thrombocytopenia (ITP) is a disease caused by autoantibodies forming against platelets and T cell dysregulation and is characterized by platelet count falling below 100 × 10⁹/L. Corticosteroids remain as the first-line of treatment, but in the light of recent developments, thrombopoietin receptor agonists are gradually replacing splenectomy in steroid-dependent or refractory patients. In this study, it was aimed to retrospectively evaluate the efficacy, safety and side-effect profile of eltrombopag treatment for chronic ITP. A total of 23 chronic ITP patients treated with eltrombopag from two health institutions in Istanbul were evaluated retrospectively. Overall response rate (partial or complete) was 87%, complete response rate was 78.3%, and the median time from treatment until reaching platelet counts above 50 × 10⁹/L was 14 days (min-max: 4-126). Treatment was discontinued in four patients due to persistent response, two of these were still fully responsive. During treatment, one patient developed basal cell carcinoma, and another developed chronic myelomonocytic leukemia. Although its long-term side effects are not yet known, eltrombopag is a very effective treatment option in ITP and may provide favorable outcomes in patients.

Comparison of Splenectomy and Eltrombopag Treatment in the Second-Line Treatment of Immune Thrombocytopenic Purpura

Objective:

Primary immune thrombocytopenia (ITP) is an acquired autoimmune disease characterized by isolated thrombocytopenia. While first-line treatments focus on inhibiting autoantibodies and platelet destruction, second- and third-line treatments include splenectomy and thrombopoietin receptor agonists. In this study, we aimed to compare the efficiency and toxicities of splenectomy and eltrombopag as second-line treatments in ITP.

Materials and Methods:

We retrospectively analyzed patients who were diagnosed with ITP and followed between 2015 and 2020. Patients who underwent splenectomy or received eltrombopag treatment as second-line or further therapy were included. For subgroup analyses, patients were further stratified according to whether they received eltrombopag in the second or third line of treatment.

Results:

There were 38 patients in the splenectomy group and 47 patients in the eltrombopag group. The mean age of patients in the splenectomy and eltrombopag groups was 43.2 and 50.5 years, respectively. Time to response was significantly shorter in the splenectomy arm (p=0.001). However, response rates at the 3^rd, 6^th, 12^th, and 24^th months did not exhibit a statistically significant difference between groups; nor did total duration of response and adverse events. Response rates at the 1^st, 3^rd, 6^th, 12^th, and 24^th months and the total duration of response did not exhibit a statistically significant difference between eltrombopag subgroups. Eltrombopag treatment was ceased for 20 patients after a median of 54.1 months (range: 1-151). Among them, 12 patients (60%) did not experience a loss of response.

Conclusion:

Comparing the splenectomy and eltrombopag arms, even though time to achieve response was in favor of the splenectomy group, this advantage disappeared when overall response rates and response rate at the 2^nd year were considered. Using eltrombopag in the second or third line of therapy does not yield any difference in terms of time to achieving response.

A Real-life Turkish Experience of Venetoclax Treatment in High-risk Myelodysplastic Syndrome and Acute Myeloid Leukemia

INTRODUCTION

Venetoclax is a selective B-cell lymphoma 2 (BCL2) inhibitor, which is approved to treat elderly patients with newly diagnosed acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS) in combination with either low-dose cytarabine (ARA-C) or hypomethylating agents. We aimed to collect and share data among the efficacy and safety of venetoclax both as a monotherapy or in combination with other drugs used to treat high-risk MDS or AML.

MATERIALS AND METHODS

A total of 60 patients with a median age of 67 (30-83) years from 14 different centers were included in the final analysis. Thirty (50%) of the patients were women; 6 (10%) of the 60 patients were diagnosed with high-risk MDS and the remaining were diagnosed with AML.

RESULTS

The best objective response rate (complete remission [CR], complete remission with incomplete hematological recovery (CRi), morphological leukemia-free state [MLFS], partial response [PR]) was 35% in the entire cohort. Best responses achieved during venetoclax per patient number were as follows: 7 CR, 1 CRi, 8 MLFS, 5 PR, and stable disease. Median overall survival achieved with venetoclax was 5 months in patients who relapsed and not achieved in patients who were initially treated with venetoclax. Nearly all patients (86.7%) had experienced a grade 2 or more hematologic toxicity. Some 36.7% of these patients had received granulocyte colony stimulating factor (GCSF) support. Infection, mainly pneumonia (26.7%), was the leading nonhematologic toxicity, and fatigue, diarrhea, and skin reactions were the others reported.

CONCLUSION

Our real-life data support the use of venetoclax in patients with both newly diagnosed and relapsed high-risk MDS and AML.

Beta Thalassemia Minor: Patients Are Not Tired but Depressed and Anxious

OBJECTIVE

We aimed to investigate whether the severity of fatigue and the incidences of depression and anxiety of patients with beta thalassemia minor (BTm) are different from healthy individuals using the Fatigue Severity Scale (FSS) and Hospital Anxiety and Depression Scale (HADS).

SUBJECTS AND METHODS

BTm patients who were followed at the University of Health Sciences Istanbul Training and Research Hospital Hematology Clinic between 2016 and 2017 and who had normal biochemical parameters, thyroid function tests and C-reactive protein levels, and did not use any medications, consume alcohol or tobacco, have any chronic diseases or sleep disturbances were included in the study. Healthy control subjects who were matched with age, sex, marital status, educational status, and body mass index (BMI) were also included for comparison.

RESULTS

Thirty-nine BTm patients and 25 healthy controls were included in the study. The BTm and the control groups were comparable in terms of gender, age, BMI, educational status and marital status (p = 0.368, 0.755, 0.851, 0.785, and 0.709, respectively). FSS score was ≥4 in 23 (59.0%) BTm subjects and in 15 (60%) control subjects (p = 1.0). HADS anxiety score was ≥10 in 20 (51.3%) BTm subjects and in 5 (20.0%) control subjects (p = 0.018), and HADS depression score was ≥7 in 20 (51.3%) BTm subjects and in 6 (24.0%) healthy control subjects (p = 0.039).There was no correlation of hemoglobin with FSS score (p = 0.526, r = -0.105), HADS anxiety score (p = 0.703, r = -0.063), or HADS depression score (p = 0.718, r = -0.06) in the BTm group.

CONCLUSION

We found that both depression and anxiety were higher in BTm patients than in healthy individuals, but this difference was not feasible for fatigue.

How Does 2016 WHO Criteria for Polycythemia Vera Contribute to Our Daily Practice? A Single-Center Study from Turkey

Background: We evaluated the frequency of subnormal erythropoietin levels, Janus kinase 2 (JAK2) V617F positivity and polycythemia vera (PV) in patients who did not meet World Health Organization (WHO) 2008 criterion for hemoglobin levels but were suggested to be investigated for PV in 2016 revision. Materials and Methods: We assessed the data of 92 patients who were further evaluated with JAK2V617F mutation and serum erythropoietin (EPO) levels and bone marrow biopsy, if necessary. We also compared this patient group with 20 patients whose Hgb>18.5 g/dL for men and >16.5 g/dL for women. Results: Nine patients (45%) in the higher hemoglobin group were JAK2V617F positive, while 4 patients (4.3%) in the lower hemoglobin group were JAK2V617F positive (p<0.001). The number of patients with serum EPO levels <4.3 mIU/mL was significantly higher in the higher hemoglobin group (n=13, 65%) than the lower hemoglobin group (n=7, 7.6%) (p<0.001). Finally, the number of patients who received a diagnosis of PV was significantly higher in the higher hemoglobin group (n=13, 65%) than the lower hemoglobin group (n=9, 9.8%) (p<0.001). Conclusion: We found a substantial increase in patients who were candidates for testing for PV with the introduction of WHO 2016 criteria; these patients were diagnosed with PV with a rate (9.8%) that cannot be underestimated.

Lenalidomide Plus Decitabine Treatment in a Myelodysplastic Syndrome Patient With Deletion 5q and Excess Blasts

This is the first case of decitabine plus lenalidomide treatment for a myelodysplastic syndrome (MDS) patient with 5q deletion (del(5q)) and elevated number of blasts. Upon bone marrow aspiration and biopsy with conventional cytogenetical studies she was diagnosed with MDS with del(5q) and refractory anemia with excess blasts (RAEB-1). Decitabine was started at a daily dose of 20 mg/m² 1 - 5 days and lenalidomide was started at daily doses of 10 mg 6 - 20 days a month. After two cycles, her hemoglobin level increased and transfusion dependency ceased. After four cycles, bone marrow aspiration showed blast ratio of < 5%. Decitabine and lenalidomide were applied for three more cycles. Decitabine was terminated after seven cycles and lenalidomide has been continued for 12 months. Latest blood values (February 2020) were as follows: white blood cells (WBCs) of 8,670/mm³, neutrophil count of 3,470/mm³, hemoglobin (Hb) level of 11.7 g/dL and platelet count of 203,000/mm³, and the patient continues to follow-up without treatment. In conclusion, combination of lenalidomide and decitabine seems to be an effective treatment modality without notable side effects in MDS patients with del(5q) and excess blasts. The efficacy of this combination should be validated with studies including large patient groups and with longer follow-up periods.

Evaluation of the Reliability of Interim PET/CT in the Hodgkin Lymphoma

INTRODUCTION

Positron-emission tomography (PET)/computerized tomography (CT) with 18F-fludeoxyglucose (FDG) has been come into use for risk assessment of Hodgkin lymphoma (HL) patients in recent years. The aim of our study is to evaluate the reliability of interim PET results according to Deauville score (DS), and also to compared PET findings with tumor reduction on CT.

METHODS

Forty-two HL patients (median 39, range 19-75 y, 27 M, 15 F) were retrospectively evaluated with pre, interim and post-treatment PET/CT imaging. PET/CT imaging was obtained 60 min after the intravenous administration of 3.7-5.2 MBq/kg 18F-FDG.

RESULTS

The negative predictive value of the interim PET was 89%. Four (10.5%) of the 38 interim PET-negative patients became post-treatment PET-positive. According to CT, 15 patients were in complete remission (CR), 27 (64.6%) patients were in partial remission (PR) or stable disease (SD).

CONCLUSION

The negative predictive value of interim PET was not satisfactory considering the treatment rate of over 80% of HL. Additionally, high rate of interim PET-negative patients' conversion to PET-positive post-treatment state was considered as unexpected.

Prevalence of inflammatory back pain and radiologic sacroiliitis is increased in patients with primary Sjögren's syndrome

Introduction

The prevalence of Sjögren's syndrome (SS) in patients with the diagnosis of SpA has been reported to be higher than normal population. Yet, the vice-versa is unclear. In this study, we aimed to investigate the prevalence of IBP, radiologic sacroiliitis and SpA in patients with primary SS.

Methods

85 patients followed at the rheumatology clinics of the Marmara and Kocaeli Universities with the diagnosis of primary SS between November 2011 and August 2012 were included in this study. The control group consisted of 100 age-and gender-matched patients. Inflammatory back pain and axial SpA were diagnosed according to the assessment of spondylo arthritis International Society (ASAS) criteria.

Results

83 patients were (97%) female and 2 (3%) were male. Mean age of the patients was 49.1 (±11) years. Mean disease duration was 7.3 (±4) years. The patient and control groups were comparable in terms of age and gender (p > 0.05). Inflammatory back pain was observed in 21 (24.7%) of 85 primary SS patients and in 4 (4%) of 100 control subjects (p < 0.001), radiographic sacroiliitis was demonstrated in 9 (10.5%) of primary SS patients and 2 (2%) of the control subjects (p = 0.025). Remaining SpA findings were not encountered in either group.

Conclusion

inflammatory back pain and radiologic sacroiliitis is increased in patients with primary SS. Whether IBP, SI joint inflammation and radiologic sacroiliitis is due to the co-existence of SpA and primary SS or IBP is an underdiagnosed clinical feature of SS deserves further studies of large patient numbers.

Stem cell mobilization kinetics in elderly patients with multiple myeloma

In this study, we aimed to investigate whether the procedure and product kinetics differ according to age groups in advanced-age MM patients who underwent autologous HSCT. 59 patients who underwent autologous HSCT were retrospectively analyzed. Then, the patients were divided into two groups as 60-65 years and ≥65 years. It was significantly lower in ≥65 years group (p = 0.008) and proportionally, the procedure duration was also significantly shortened in this group (p = 0.013). Total number of collected CD34 positive stem cells was 6.20 × 106 (±3.83) in 60-65 years group while it was 5.51 × 106 (±2.48) in ≥65 years group with no statistically significant difference (p = 0.825). In conclusion, there was no significant difference in terms of the number of collected CD34-positive stem cells in this study that investigates the mobilization data, procedure and product kinetics, we think that successful stem cell mobilization can be performed in appropriately selected patients regardless of age.

Autologous stem cell transplantation and stem cell mobilization kinetics in elderly patients with B cell non-Hodgkin lymphoma

As known, the world population is aging and as the life span increases the number of advanced-age lymphomas also shows an upward trend. Autologous hematopoietic stem cell transplantation (HSCT) is the standard treatment modality in chemotherapy-sensitive relapsed or refractory aggressive lymphomas. Increased morbidity and mortality related to both the transplant itself and comorbid diseases can be observed in elderly lymphoma patients. Patients who are 65 years or older and underwent autologous HSCT with B-cell non-Hodgkin lymphoma were retrospectively included in our study. In terms of survival analysis, median follow-up was 34.5 months (8-159) while the overall survival (OS) was 58%. In the univariate analysis of prognostic data in OS, patients who were referred to transplantation with complete response had a statistically significant survival advantage (p=0.043). In terms of the effect of pre-transplant conditioning regimens on survival, BEAM regimen yielded better results, though not statistically significant. Age, number of chemotherapy cycles received before mobilization and radiation therapy had no significant effect on the CD34 (+) cell count in the final product (p=0.492, 0.746 and 0.078 respectively). In conclusion, autologous HSCT is a practicable treatment modality that provides survival advantage in suitable advanced-age patients with a diagnosis of B-cell non-Hodgkin lymphoma.

Evaluation of neutrophil-lymphocyte ratio in patients with early-stage mycosis fungoides

Neutrophil-lymphocyte ratio (NLR), an indicator of inflammation, has been lately demonstrated as a prognostic factor and an indicator of disease activity in various diseases. However, the effects of NLR have not been investigated in mycosis fungoides (MF) patients yet. The aim of this study is to investigate the relationship between the NLR and treatment demand (systemic PUVA and/or chemotherapy), time to treatment, progression in stage, and time to progression in stage in MF patients. The data of 117 patients, who were followed with the diagnosis of MF at the Department of Dermatology in Istanbul Training and Research Hospital between April 2006 and January 2016, were analyzed retrospectively. The cutoff score for NLR was determined as 2 according to the median NLR level which was 1.96. At the time of diagnosis, the median age of patients was 54 years (range, 21-90) with 62 (53 %) female and 55 (47 %) male. Seventy-seven (65.8 %) patients required treatment during follow-up. Sixty-three (53.8 %) patients showed progression in disease stage. There was no significant difference in treatment demand, time to treatment, progression in stage, and time to progression in stage in patients with a NLR ≥ 2 and NLR < 2 (p = 0.331, 0.987, 0.065, and 0.119, respectively). It seems that there is no association between the NLR and treatment demand, time to treatment, progression in stage, and time to progression in stage in MF patients.

T-cell acute lymphoblastic leukemia with co-expression of CD56, CD34, CD117 and CD33: A case with poor prognosis

T-cell acute lymphoblastic leukemia (ALL) is an aggressive hematological malignancy, accounting for ~25% of all adult cases of ALL. We herein report a case of T-cell ALL exhibiting aberrant CD34, CD56, CD33 and CD117 expression in addition to T-cell markers, which did not respond to induction treatment. A 55-year-old woman was admitted to our hospital with a sore throat unresponsive to medication for 1 month. The laboratory examination revealed pancytopenia and the peripheral blood smear examination revealed blast cells. On flow cytometric analysis, the blast cells were found to be positive for cytoplasmic CD3, CD2, CD5, CD7, CD34, CD56, CD33 and CD117, and negative for myeloperoxidase, CD13, CD11b, CD15, CD19, CD79a, CD22 and CD10. The patient was diagnosed with T-cell ALL according to the 2008 World Health Organisation classification. The patient did not respond to Hyper-cyclophosphamide, vincristine, adriamycin and dexamethasone (CVAD) course A treatment and succumbed to the disease during Hyper-CVAD course B treatment. To the best of our knowledge, this is the first report of aberrant co-expression of the natural killer cell marker CD56, myeloid cell markers CD117 and CD33 and stem cell marker CD34 in a patient with T-cell ALL. This appears to be associated with an unfavorable outcome, despite the use of intensive chemotherapy.

A HHV-8 positive, HIV negative multicentric Castleman disease treated with R-CEOP chemotherapy and valganciclovir combination

Multicentric Castleman disease (MCD) is a lymphoproliferative disorder characterized by systemic symptoms like recurrent lymphadenopathy, fever and hepatosplenomegaly. Human herpes virus 8 (HHV-8) can be associated with MCD whether the patient is infected with human immunodeficiency virus (HIV) or not. A 59-year-old male patient presented with fatigue, drowsiness and enlarged lymph nodes. Thoracic and abdominal computed tomography showed enlarged mediastinal, axillary, paracardiac, paraaortic, celiac, mesenteric, obturator and inguinal lymph nodes concomitant with enlarged liver and spleen. Cervical lymph node biopsy revealed HHV-8 positive plasma cell MCD. The patient's tests were negative for HIV. R-CEOP (rituximab, cyclophosphamide, etoposide, vincristin, prednisolone) and valganciclovir treatments were started simultaneously. After sixth cycle of R-CEOP, the patient achieved unconfirmed complete remission. Rituximab combined with CEOP protocol and antiviral therapy against HHV-8 might be an effective therapeutic approach without a considerable side effect for HHV-8-positive HIV-negative MCD patients.

Preclinical evaluation of two human anti-hepatitis B virus (HBV) monoclonal antibodies in the HBV-trimera mouse model and in HBV chronic carrier chimpanzees

Two human monoclonal antibodies (mAbs) against hepatitis B surface antigen (HBsAg) generated in the Trimera mouse system are described. Both mAbs 17.1.41 and 19.79.5 are of the IgG1 isotype and have high affinity constants for HBsAg binding in the range of 10(-10) mol/L. Monoclonal antibody 17.1.41 recognizes a conformational epitope on the a determinant of HBsAg whereas mAb 19.79.5 recognizes a linear one. The 2 mAbs bind to a panel of hepatitis B virus (HBV) subtypes with distinct patterns. The neutralizing activity of these antibodies was tested in 2 different animal model systems. Administration of each mAb to HBV-Trimera mice, a system that provides a mouse model for human hepatitis B infection, reduced the viral load and the percentage of HBV-DNA-positive mice in a dose-dependent manner. These 2 mAbs were more effective than a polyclonal antibody preparation (Hepatect; Biotest Pharma, Dreieich, Germany) in both inhibition of HBV liver infection and reduction of viral load. A single administration of a mixture of these mAbs into HBV chronic carrier chimpanzees resulted in immediate reduction in HBsAg levels followed by recurrence to initial levels within few days. Thus, these mAbs may be potential candidates for preventive therapy or in combination with other antiviral agents against HBV. Further studies in humans are needed to assess these mAbs in various clinical indications.

The hepatitis B virus-trimera mouse: a model for human HBV infection and evaluation of anti-HBV therapeutic agents

Previous studies have demonstrated the feasibility of implantation of human blood cells or tissues in lethally irradiated mice or rats, radioprotected with SCID mouse bone marrow cells: The Trimera system. In the present study, we describe the development of a mouse Trimera model for human hepatitis B virus (HBV) infection. In this model, viremia is induced by transplantation of ex vivo HBV-infected human liver fragments. Engraftment of the human liver fragments, evaluated by hematoxylin-eosin staining and human serum albumin mRNA expression, was observed in 85% of the transplanted animals 1 month postimplantation. Viremia levels were determined in these mice by measuring serum HBV DNA using polymerase chain reaction (PCR), followed by dot-blot hybridization. HBV DNA is first detected 8 days after liver transplantation. Viremia attains a peak between days 18 and 25 when HBV infection is observed in 85% of the transplanted animals. The HBV-Trimera model was used to evaluate the therapeutic effects of human polyclonal anti-HBs antibodies (Hepatect) and of two reverse-transcriptase inhibitors, lamivudine (3TC) and beta-L-5-fluoro-2',3'-dideoxycytidine (beta-L-5FddC). Treatment of HBV-Trimera mice with these drugs effectively reduced both the percentage of infected animals and the viral load in their sera. Treatment cessation resulted in rebound of viral load, indicating HBV replication upon drug withdrawal. These results show that the HBV-Trimera model represents a novel experimental tool for simulating human HBV infection and evaluating potential anti-HBV therapeutic agents.

Cloning and characterization of the promoter for the human complement factor I (C3b/C4b inactivator) gene

Complement factor I is a serine proteinase that regulates the classical and alternative pathways of complement by cleaving C3b and C4b and preventing the assembly of C3 and C5 convertase enzymes. In order to understand the regulation of factor I gene expression in liver cells, 4kb of the 5' flanking region of the gene was cloned, and the 1474-bp 3'-end was sequenced and shown to contain a number of transcription factor consensus sequences. A major and two minor transcription start sites were identified, respectively, at 152, 178, and 198bp upstream of the translation start site by primer extension analysis. The transcriptional activity of the 1474-bp fragment was analyzed by fusion of 5' deletion constructs to a cat-encoding gene expression vector and transient transfections into Hep G2 cells. A 273-bp fragment located at -112 to +161 relative to the major transcription start site was sufficient for promoter activity. The 3' fragment spanning +3 to +161 and containing a TATA-like element did not demonstrate promoter activity, suggesting that the core promoter resides in a 115-bp sequence located between -112 and +3. This region contains an Inr-like element overlapping the major cap site and a CTF-NF1 element, two potential CCAAT boxes and an AP-2 element partially overlapping an Sp-1 site. Thus, factor I promoter may belong to the TATA-less Inr-driven class II promoters whose transcription is regulated by Sp-1. The transcriptional activity of the 1474-bp 5' flanking fragment was upregulated by PMA, IL-6 and TNF-alpha, suggesting that factor I may be an acute phase reactant.

Human monoclonal antibodies specific to hepatitis B virus generated in a human/mouse radiation chimera: the Trimera system

An approach to develop fully human monoclonal antibodies in a human/mouse radiation chimera, the Trimera system, is described. In this system, functional human lymphocytes are engrafted in normal strains of mice which are rendered immuno-incompetent by lethal total body irradiation followed by radioprotection with severe combined immunodeficient (SCID) mouse bone marrow. Following transplantation, human lymphocytes colonize murine lymphatic organs and secrete human immunoglobulins. We have established this system as a tool to develop fully human monoclonal antibodies, and applied it for the generation of monoclonal antibodies specific for hepatitis B virus surface antigen. A strong memory response to hepatitis B surface antigen was elicited in Trimera engrafted with lymphocytes from human donors positive for antibodies to hepatitis B surface antigen. The human specific antibody fraction in the Trimera was 10(2)-10(3)-fold higher as compared with that found in the donors. Spleens were harvested from Trimera mice showing high specific-antibody titres and cells were fused to a human-mouse heteromyeloma fusion partner. Several stable hybridoma clones were isolated and characterized. These hybridomas produce high-affinity, IgG, anti-hepatitis B surface antigen antibodies demonstrating the potential of the Trimera system for generating fully human monoclonal antibodies. The biological function and the neutralizing activity of these antibodies are currently being tested.

Thymocyte-directed enhancement of apoptosis via soluble factor(s) derived from a cortical and a medullary thymic epithelial cell line

Apoptosis of murine thymocytes was examined either in intact fetal thymus lobes or in thymus cell suspensions, both cultured alone or in the presence of either a cortical (TEC 1.4) or a medullary (TEC 2.3) thymic epithelial cell line. Both TECs induced a pronounced increase of apoptosis in 24-h cultivated single thymus cell suspensions but not in spleen or bone marrow cell cultures. Co-culture of thymocytes with murine fibroblasts did not enhance apoptosis of the thymus cells. A similar enhancement of thymocyte apoptosis was observed with dialysed culture supernatants derived from both TEC lines, the active component(s) having a molecular weight of > 30 kDa. In contrast, the cortical TEC 1.4 had a pronounced apoptosis inducing effect on intact fetal thymus lobes cultivated for six days, whereas the medullary TEC 2.3 had only a marginal influence. TEC 1.4 also induced a significant alteration in the ratio of CD4+CD8+ to CD4-CD8- cells. It is concluded that both the cortical and medullary epithelial cell lines are able to induce thymocyte apoptosis but that a large proportion of the cells within the intact thymus stroma is refractory to the respective signal(s) of the medullary epithelial cell line.

MHC-linked colonization of the thymus and thymocyte development: effects of mature T lymphocytes

Effects of mature T lymphocytes on thymic colonization by lymphohemopoietic cells were investigated in an in vitro experimental model, using a variety of experimental strategies. Lymphoid-depleted fetal thymus (FT) explants (C57BL/Ka, Thy1.1, H-2b) were incubated with bone marrow (BM) cells from syngeneic (C57BL/Ka; SBM) and allogeneic (BALB/c, Thy1.2, H-2d; ABM) donors. Cocultures of FT with SBM and ABM, depleted of Thy1+ or of CD3+ cells, resulted in equal proportions of lymphocytes from both BM donors. When peripheral blood lymphocytes (PBL) from synegenic or semi-allogeneic donors (F1[C57BL/Ka x C57BL/6J], Thy1.1/Thy1.2); or F1[C57BL/Ka x BALB/c], Thy1.1/Thy1.2, respectively) were added to these cultures, the total lymphocyte count per thymic lobe decreased and a developmental preference of the SBM-derived cells, as compared to the ABM-derived cells, was noted. Cells of the PBL types were also observed in the cultures. Cocultures of FT with ABM and PBL showed reduced proportions of ABM-derived cells and occurrence of cells of the PBL type. Finally, FT explants partially depleted of lymphocytes by irradiation (6 Gy), were cocultured with PBL from either syngeneic or allogeneic donors. In the presence of syngeneic PBL, the total number of cells and the proportion of double-positive (CD4+CD8+) T cells were similar to those in the FT cultured by itself, whereas in the presence of allogeneic PBL these values were reduced. The study suggests that mature T lymphocytes may play a role in the developmental processes in the thymus, and points to MHC-linked selective effects.

MHC recognition in colonization of the thymus by bone marrow cells

The role of major histocompatibility complex (MHC) class I and II molecules in the process of colonization of the thymic microenvironment by lymphohemopoietic cells was analyzed in an in vitro experimental model. When lymphoid-depleted fetal thymus (FT) explants were cocultured with a mixture of bone marrow (BM) cells, from donors syngeneic and allogeneic to the FT, the cells syngeneic to the FT showed a developmental preference. Treatment of these cocultures with antibodies to MHC class I (H-2D, H-2K) or class II (I-E, I-A) molecules of the syngeneic cells led to preferential development of the allogeneic donor type cells. Incubation of either the FT or the BM cell inoculum with the antibodies prior to coculture indicated that the effect was exerted on the BM cells rather than on the thymic stroma.

Aging in the T lymphocyte compartment. A developmental view

A decline in the capacity of bone marrow cells to differentiate to T lymphocytes was found when cells from young and old donors were seeded onto an alymphoid fetal thymus. A step-by-step analysis of cell-cell interactions of the lymphohemopoietic cells and the thymic stroma indicated an effect of age on a variety of cell differentiation parameters. These included a decrease in the affinity of bone marrow cells to the stroma, and in their capacity to compete with the thymic lymphoid resident cells on colonization of the thymus. There was a significant decrease in the ability of cells of old donors to replicate sequentially within the thymic microenvironment. There was a reduced capacity of bone marrow cells from aging mice to express a developmental preference after seeding onto a syngeneic fetal thymus in a mixture with cells from allogeneic donors. We addressed the question whether the aging thymus contains increased levels of immature cells that fail to differentiate in the involuted thymic microenvironment by seeding thymocytes from young and old donors onto the fetal thymic stroma. The values of T cells that developed from the old donor inoculum were lower under these conditions. Our studies suggest that at least some of the manifestations of aging in the T cell compartment are related to developmentally programmed events in the lymphohemopoietic cell compartment.

Expression of the amiloride-blockable Na+ channel by RNA from control versus aldosterone-stimulated tissue

The amiloride-blockable Na+ channel was expressed in Xenopus oocytes injected with total RNA isolated from the toad urinary bladder. This system was used to investigate mechanisms that mediate the natriferic action of aldosterone. Incubation of the epithelium with aldosterone for 3 h doubled its channel activity but did not increase the ability of isolated RNA to express functional channels in oocytes. A 20-h incubation with the hormone produced an additional increase of Na+ transport across the intact epithelium and also augmented the channel activity expressed in oocytes by nearly 10-fold. The data are in agreement with our model that aldosterone enhances the apical Na+ permeability of tight epithelia by a short term activation of pre-existing channels, followed by chronic induction of new channel protein. Blocking methyl transfer reactions, previously shown to inhibit the natriferic action of aldosterone in tight epithelia, did not alter the basal or aldosterone-induced response in oocytes.

NaCl-dependent expression of amiloride-blockable Na+ channel in Xenopus oocytes

RNA was isolated from chicken lower intestine (both colon and coprodeum) and injected into Xenopus oocytes. 22Na+ fluxes measured after 1-4 days demonstrated the induction of an amiloride-blockable pathway. The Na+ transporter expressed by the exogenous RNA had a high affinity to amiloride (inhibitory constant less than 0.1 microM), but was insensitive to ethylisopropyl amiloride, i.e., it is likely to be the apical Na+ channel. Functional channels were readily expressed in oocytes injected with RNA derived from chickens fed a low-NaCl diet. On the other hand, no channel activity was detected in oocytes injected with RNA isolated from chickens fed a high-NaCl diet. Thus the previously reported regulation of transport by the dietary NaCl intake involves modulations in the level of mRNA that codes either for the Na+ channel or a posttranscriptional regulator of the channel.

Quantitative analysis of bone marrow thymic progenitors in young and aged mice

Our studies on the capacity of bone marrow (BM) to generate T lymphocytes in aging have revealed that under the competitive conditions of thymic reconstitution, cells of aged mice are significantly inferior to those of the young. The present study was designed to further investigate the basis of this age-related change. Two mechanisms were considered: (a) The potential of BM-derived T cell precursors from aged mice to proliferate and differentiate in the thymic microenvironment is impaired. (b) The frequency of T cell precursors is reduced in BM of aged mice, thus affecting their ability to compete efficiently in reconstituting the thymus. These possibilities were studied in vitro by colonizing thymocyte-depleted fetal thymic lobes with BM cells from aged (24-month) and young (3-month) C57BL/6 mice. By determining the cell cycle duration of BM-derived cells which have seeded the thymic lobes, we found that cells originating from aged mice proliferate in the thymus at the same rate as those from young mice. Reconstitution with limiting numbers of BM cells indicated that the frequency of thymic progenitors in the BM is significantly reduced in aged as compared to young mice. We thus conclude that aging is associated with a quantitative reduction in the frequency of thymic progenitors in the BM.

Selective accumulation of lymphocyte precursor cells mediated by stromal cells of hemopoietic origin

Thymocytes were propagated in long-term cultures supported by stromal cells of both bone marrow and thymus origin. Interleukin 2 (IL-2) supplementation augmented the cell yield and allowed detailed phenotype analysis. Within 2-3 months of culture a cell population was selected in which the expression of Thy-1 antigen persisted, CD4 and CD8 antigens gradually declined, and Pgp-1 antigen, found on less than 5% of fresh thymocytes, was strongly increased. This cultured cell population (Thy-1.2 origin) contained no detectable spleen colony-forming units (CFU-S) but efficiently repopulated the thymus of Thy-1.1-irradiated congenic mice, indicating the precursor T-cell nature of the population. Upon removal from the stroma, the T cells exhibited poor cytotoxicity towards syngeneic tumor cells. Further propagation with IL-2 in the absence of stroma resulted in the acquisition of cytotoxic ability. Replacement of the horse serum used in the above experiments with fetal calf serum resulted in accumulation of cells expressing B220 antigen. This experimental model provides the means to maintain lymphocyte precursor cells in long-term culture and to further study their differentiation in the absence of stroma, both in vitro and in vivo.

Syngeneic preference manifested by thymic stroma during development of thymocytes from bone marrow cells

The question whether major histocompatibility complex (MHC) recognition is expressed in interactions between thymocyte progenitors and thymic stroma cells was investigated in an organ culture system, in which inductive interactions between thymic stroma cells and thymocyte progenitors of different MHC haplotypes could be measured. Thymocyte-depleted fetal thymuses were reconstituted with mixtures of syngeneic and allogeneic bone marrow cells, which also differed in their Thy-1 allele. The relative repopulating ability of the cells was estimated by determining the percentage of emerging Thy-1.1+ vs. Thy-1.2+ thymocytes. Similar values of Thy-1+ cells of the bone marrow donor type developed when the thymus were reconstituted by bone marrow from donors which were either syngeneic or allogeneic to the thymic explants. However, when a 1:1 mixture of syngeneic and allogeneic cells was applied to the thymus, a syngeneic preference was manifested in development of Thy-1+ cells. When mixtures of bone marrow cells from C57BL/Ka (Thy-1.1) and B10.A MHC-congenic (Thy-1.2) mice were used, this developmental preference was found to map to the I-E region. Thymocytes derived from bone marrow cells allogeneic to the stroma, seeded on their own, manifested an advantage over allogeneic bone marrow cells from a different MHC haplotype, in a secondary reconstitution. This suggested that allogeneic bone marrow progenitor cells can be "educated" by the host thymic stroma to behave, in the competitive reconstitution, like syngeneic cells.

Age-related changes in the capacity of bone marrow cells to differentiate in thymic organ cultures

The capacity of the bone marrow to give rise to T cells in advanced age was studied in vitro by reconstituting fetal thymic lobes from 14-day C57BL/Ka (Thy-1.1) mice with bone marrow cells from old (24-month) or young (3-month) C57BL/6 (Thy-1.2) mice. The use of these congenic strains enabled distinguishing between donor and host contribution to the developing T cells. We found that bone marrow cells from aged mice maintained their capacity to reconstitute fetal thymic explants and to differentiate into various T-cell subsets as assessed by distinct T-cell-specific surface markers (Thy-1, Lyt-1, Lyt-2, and L3T4) and functions (concanavalin A-induced proliferative and cytotoxic responses). However, when mixtures of old and young bone marrow cells reconstituted fetal thymic explants, the cells of old mice were less efficient than those of young in their capacity to give rise to T cells. These results indicate that bone marrow cells from aged mice can reconstitute the thymus and differentiate into T cells; however, their reconstituting capacity is inferior to that of bone marrow cells from young mice.

Ontogeny of T cells: development of pre-T cells from fetal liver and yolk sac in the thymus microenvironment

The patterns of development of T cells from the very early stem cells that settle in the embryonic thymus have been studied. For this purpose, mouse embryonic thymuses (14 days) depleted of thymocytes were reconstituted with hemopoietic stem cells from fetal liver (FL) and yolk sac (YS) and T-cell development was followed in vitro in organ culture. It was found that cells derived from FL and YS of 10- to 14-day-old embryos were capable of reconstituting depleted thymic explants and exhibiting membrane markers in a pattern similar to that of thymocytes developing in intact thymic explants. Furthermore, these cells responded to concanavalin A in proliferative and cytotoxic assays as measured by limiting-dilution analysis. Thus, lymphohemopoietic stem cells emerging in the embryo prior to thymus lymphoid development are capable of differentiation in the thymus microenvironment into T cells, identified by phenotypic markers and functions that are characteristic of cells developing in the intact embryonic thymus.

Inhibition of the formation of lipid-linked intermediates in normal and transformed cells by a purified tunicamycin homologue

The effects of a purified homologue of tunicamycin (B2-tunicamycin) on the biosynthesis of lipid-linked intermediates participating in protein glycosylation in normal embryonic fibroblasts, 3T3 and virally transformed (simian virus 40 and polyoma virus) mouse fibroblasts grown in culture were investigated. Long incubations (20 h) with the antibiotic caused a higher degree of inhibition of sugar incorporation into glycoproteins in transformed cells. However, the formation of lipid-linked intermediates was inhibited to a similar level in both cell types. When time dependent inhibition experiments were carried out using transformed cells, an earlier and stronger inhibition of the formation of lipid-oligosaccharides occurred (70% inhibition at 30 min). In 3T3 cells, prolonged incubation (6-8 h) was necessary in order to reach a similar degree of inhibition. Formation of lipid-sugar was also inhibited to a greater extent by B2-tunicamycin in transformed cells. This inhibition was not clearly time dependent. Analysis of the newly synthesized glycolipids in 3T3 and in transformed cells after B2-tunicamycin treatment have shown reduction in dolichyl-P-P-sugars as well as in other glycolipids. Dimethylsulfoxide (10%) and linoleic acid (0.5 mg/ml) markedly increased the level of tunicamycin activity in 3T3 cells while phosphatidylcholine (2 mg/ml) partially reversed it. The stronger and faster inhibition of the formation of lipid intermediates of the dolichyl-phosphate cycle caused by B2-tunicamycin in transformed cells, described here for the first time, may therefore be due to differences in penetration of the antibiotic into these cells.

Differentiation and activity of mast cells following immunization in cultures of lymph-node cells

An extensive clonal differentiation into mast cells from primitive blast cell precursors occurred when lymph node cells obtained from mice immunized with horse serum were cultured on mouse embryonic skin monolayers. Horse serum was always present in the culture as a constituent of the nutritional medium. Mast cells developed to lesser extent also in cultures prepared from non-immunized mice. However, a clear difference in mast cell-granule ultrastructure and in histamine content was noted between the two. In cultures of lymph nodes cells from non-immunized mice the granules were tiny and uniform in size and in staining density; whereas granules in the immune cultures were larger and non-uniform in size and in staining density, and the intragranular organization manifested alterations of various forms. The content of intracellular histamine per 10(6) mast cells was about equal in both cultures. However, much more free histamine (per 10(6) mast cells) gradually accumulated in cultures of the immune lymph node cells, indicating higher rates of synthesis and release of histamine. The mast cells were readily degranulated by heat-inactivated (IgG1) sera of the mice used as donors of the lymph node cells. 92% of the mast cells were degranulated and as much as 80% of the histamine was released. The degranulation was accompanied by an immediate (albeit reversible) response of the fibroblast cells in the monolayer. A shift of the well-stretched cytoplasm of the fibroblasts opened numerous 'window' over the whole monolayer. The degranulated mast cells survived the process and could be maintained further in the cultures. Moreover, they were capable of repeated degranulation, releasing 50% of their histamine, even after four degranulation cycles performed over a 7 days' period of culture. No cytotoxic effect on the mast cells was noted and the histamine content in culture, 3 days after degranulation, seemed to be higher than in the undergranulated control cultures--suggesting an intensified rate of histamine synthesis.