Katalin Pálóczi

HIV transmission from female to male at improperly protected sexual intercourse

There is growing evidence that human immunodeficiency virus (HIV) infection can be transmitted from female to male after only 2 sexual contacts. The authors present a case in which the wife was infected with HIV in March 1986 as a result of transfusion of blood from a homosexual. She tested positive for HIV in January 1987 and in February was notified of her positive test result. The couple had had regular unprotected sexual intercourse between April 1986 and February 1987. In February 1987 the patients husband was negative for HIV infection and condom use was initiated. By October 1987 the husband was found to be seropositive for HIV. The couple reported that the condom had torn on several occasions since protected intercourse was initiated. It cannot be determined whether HIV was transmitted before February during unprotected intercourse and the husband seroconverted after the 1st blood sampling or whether HIV was transmitted after notification of the wifes seropositive status.

Soluble Jagged-1 is able to inhibit the function of its multivalent form to induce hematopoietic stem cell self-renewal in a surrogate in vitro assay

Stem cells reside in customized microenvironments (niches) that contribute to their unique ability to divide asymmetrically to give rise to self and to a daughter cell with distinct properties. Notch receptors and their ligands are highly conserved and have been shown to regulate cell‐fate decisions in multiple developmental systems through local cell interactions. To assess whether Notch signaling may regulate hematopoiesis to maintain cells in an immature state, we examined the functional role of the recombinant, secreted form of the Notch ligand Jagged‐1 during mouse hematopoietic stem cell (HSC) and progenitor cell proliferation and maturation. We found that ligand immobilization on stromal layer or on Sepharose‐4B beads is required for the induction of self‐renewing divisions of days 28–35 cobblestone area‐forming cell. The free, soluble Jagged‐1, however, has a dominant‐negative effect on self‐renewal in the stem‐cell compartment. In contrast, free as well as immobilized Jagged‐1 promotes growth factor‐induced colony formation of committed hematopoietic progenitor cells. Therefore, we propose that differences in Jagged‐1 presentation and developmental stage of the Notch receptor‐bearing cells influence Notch ligand‐binding results toward activation or inhibition of downstream signaling. Moreover, these results suggest potential clinical use of recombinant Notch ligands for expanding human HSC populations in vitro.

Inappropriate notch activity and limited mesenchymal stem cell plasticity in the bone marrow of patients with myelodysplastic syndromes

Myelodysplastic syndromes (MDSs) are a heterogeneous group of hematological disorders characterized by ineffective hematopoiesis, enhanced bone marrow apoptosis and frequent progression to acute myeloid leukemia. Several recent studies suggested that, besides the abnormal development of stem cells, microenvironmental alterations are also present in the MDS bone marrow. In this study, we have examined the relative frequencies of stem and progenitor cell subsets of MDS and normal hematopoietic cells growing on stromal cell layers established from MDS patients and from normal donors. When hematopoietic cells from MDS patients were co-cultured with normal stromal cells, the frequency of either early or late cobblestone area-forming cells (CAFC) was significantly lower compared to the corresponding normal control values in 4 out of 8 patients. In the opposite situation, when normal hematopoietic cells were incubated on MDS stromal cells, the CAFC frequencies were decreased in 5 out of 6 patients, compared to normal stromal layer-containing control cultures. Moreover, a soluble Notch ligand (Jagged-1 protein) was an inhibitor of day-35-42 CAFC when normal hematopoietic cells were cultured with normal or MDS stromal cells, but was unable to inhibit MDS stem and early progenitor cell growth (day-35-42 CAFC) on pre-established stromal layers. These findings suggest that in early hematopoietic cells isolated from MDS patients the Notch signal transduction pathway is disrupted. Furthermore, there was a marked reduction in the plasticity of mesenchymal stem cells of MDS patients compared with those of normal marrow donors, in neurogenic and adipogenic differentiation ability and hematopoiesis supporting capacityin vitro. These results are consistent with the hypothesis that when alterations are present in the myelodysplastic stroma environment along with intrinsic changes in a hematopoietic stem/progenitor cell clone, both factors might equally contribute to the abnormal hematopoiesis in MDS.

Neutralizing and complement-dependent enhancing antibodies in different stages of HIV infection

Reclustering and indirect immunofluorescence assays on MT-4 cells [carrying both CD4 and complement receptor type 2 (CR2)] were used to measure neutralizing and enhancing antibodies in sera obtained from HIV-1-infected individuals. Heat-inactivated sera were tested before and after mixing 1:1 with fresh seronegative human serum. Using heated samples, neutralizing antibodies were found in 20 out of 20 and 11 out of 19 serum samples of asymptomatic and symptomatic [AIDS, AIDS-related complex (ARC)] HIV-seropositive patients, respectively. In complement-restored samples, neutralizing activity was found in eight sera of asymptomatic patients and in none of the sera of AIDS and ARC patients; enhancing activity could be detected in four and 12 sera, respectively. A significant positive correlation was observed between the titres of neutralizing antibodies measured in the complement-restored samples and the absolute number of CD4+ lymphocytes. These findings indicate that the appearance of complement-dependent enhancing antibodies coincident with the loss of neutralizing antibodies may indicate a poor prognosis in HIV infection.

Extensive flow cytometric characterization of plasmacytoid dendritic cell leukemia cells.

Abstract:  Objectives: Accumulating evidence suggests that non‐T, non‐B cell CD4+CD56+ neoplasms with lymphoblastic morphology include clinically and immunophenotypically diverse entities. Although their cells of origin or classification are still controversial several entities clearly represent a distinct type of neoplasms that are clinically aggressive. Methods: In this work we present the immunophenotypic and genotypic features of bone marrow (BM), peripheral blood (PB), lymph node and skin lymphocytes from a patient diagnosed as plasmacytoid dendritic cell leukemia involving the skin, BM, PB, lymph nodes, liver and spleen. For determination of immunophenotypic characteristics of malignant plasmacytoid dendritic cells 73 monoclonal antibodies detecting lineage markers, chemokine receptors, cytokine receptors, activation, and co‐stimulatory molecules were used. Results and conclusion: The malignant cells proved to express CD4+, CD56+ lineage negative leukemia phenotype characteristically positive for CD36, CD38, CD40, CD45, CD45RA, CD68, CD123, CD184, HLA‐DR, BDCA2, and granzyme‐B corresponding to the preplasmacytoid dendritic cell developmental stage. The presence of CD11a/CD18, CD84, CD91, CD95, αvβ5, CDw197, and the absence of CD52 and CD133 in this case can be regarded as additional features of malignant cells. Completing the immunophenotypes with multidrug resistance function can provide additional information for characterizing pDC leukemia.

In vitro expansion of long-term repopulating hematopoietic stem cells in the presence of immobilized Jagged-1 and early acting cytokines.

There is an increasing body of evidence that suggests that genes involved in cell fate decisions and pattern formation during development also play a key role in the continuous cell fate decisions made by adult tissue stem cells. Here we show that prolonged in vitro culture (14 days) of murine bone marrow lineage negative cells in medium supplemented with three early acting cytokines (stem cell factor, Flk‐2/Flt‐3 ligand, thrombopoietin) and with immobilized Notch ligand, Jagged‐1, resulted in robust expansion of serially transplantable hematopoietic stem cells with long‐term repopulating ability. We found that the absolute number of marrow cells was increased ∼8 to 14‐fold in all cultures containing recombinant growth factors. However, the frequency of high quality stem cells was markedly reduced at the same time, except in cultures containing growth factors and Jagged‐1‐coated Sepharose‐4B beads. The absolute number of hematopoietic cells with long‐term repopulating ability was increased ∼10 to 20‐fold in the presence of multivalent Notch ligand. These results support a role for combinatorial effects by Notch and cytokine‐induced signaling pathways in regulating hematopoietic stem cell fate and to a potential role for Notch ligand in increasing cell numbers in clinical stem cell transplantation.

Immune reconstitution: an important component of a successful allogeneic transplantation

The recipients of allogeneic haematopoietic stem cell transplants are characterised by an immunodeficiency of varying severity and duration. Their immunocompromised state is due in part to: (1) an impaired recapitulation of lymphoid ontogeny, (2) a lack of sustained transfer of donor immunity, (3) the effects of graft versus host disease and its therapy, and (4) a reduction in thymic function. Recipients can have delays in the production of naive T lymphocytes following transplantation which result in defects in the production of new antigen specific T lymphocytes and an inability to produce antibodies, especially to carbohydrate antigens. T-cell proliferation as well as immunoglobulin production remains impaired usually until the second half of the first year post-transplant. Other factors that can influence immunological reconstitution include the donor-recipient relationship (histocompatible or matched unrelated donor), intervening infections and recipient age, among others.

Expression of TGFβ1 and Its Signaling Components by Peripheral Lymphocytes in Systemic Lupus Erythematosus

Transforming growth factor β1 (TGFβ1) is an important immunosuppressive cytokine. Defects in its production by lymphocytes and the failure of TGFβ1 to regulate immunological functions have been described in SLE. Expression of TGFβ1 and the related signaling pathway was studied in the peripheral lymphocytes of SLE patients. The total plasma TGFβ1 level in active and inactive SLE patients compared to healthy controls was also measured. TGFβ1 and all downstream signaling elements were expressed in normal cells. However, in more than 50% of SLE patients the isolated T cell population showed no TGFβ1 mRNA expression and at least one member of the TGFβ1 pathway was also missing (TGFβ-RI, Smad2 and Smad3) in more than half of the patients. Total plasma TGFβ1 level was increased in both active and inactive SLE groups compared to normal controls (p< 0.05). These data raise questions about the availability of TGFβ1 signaling in lymphocytes in SLE patients, however, the elevated total plasma TGFβ1 level suggests that the failure of TGFβ1 effects is not the consequence of low level of this cytokine in SLE.

Remarkably Reduced Transplant-Related Complications by Dibromomannitol Non-Myeloablative Conditioning before Allogeneic Bone Marrow Transplantation in Chronic Myeloid Leukemia

A non-myeloablative conditioning protocol containing dibromomannitol (DBM/cytosine arabinoside/cyclophosphamide) has been applied to 36 chronic myeloid leukemia (CML) patients followed by bone marrow transplantation (BMT) from sibling donors. Risk factors include: accelerated phase (10 patients), older age (17 patients over >40 years) and long interval between diagnosis and BMT (27 months on average). Severe mucositis did not occur. Venoocclusive liver disease was absent. Infectious complications were rare. Although grade II–IV acute graft-versus-host disease (GVHD) was present in 9 (25%) cases, there were only 2 serious (III–IV) ones. Chronic GVHD occurred in 25 (69%) cases, preceded by acute GVHD in 9 of the 25 affected patients. Early hematological relapse, 7–29 weeks after BMT, developed in 6 patients (17.6%). No relapse was noted in the completely chimeric patients, however molecular genetic residual disease was observed in 6 patients, in most of them after transient short-term mixed chimeric state. Overall actual survival rate is 83.3% for the 36 cases, and leukemia-free survival is 72.2% for the 34 engrafted patients.

Immunological and molecular biological identification of a true case of T-hairy cell leukaemia.

A hairy cell leukaemia (HCL) patient is presented in whom the peripheral blood mononuclear cells (PBMCs) carried suppressor T‐cell markers (CD3 +, CD2 +, CD8 + /CD4‐, CD38 +). Analysis of genomic DNA of PBMNC showed the presence of a monoclonal population of T cells, the T‐cell receptor (TCR) beta‐chain gene being rearranged on both alleles (DR/DR), while the immunoglobulin (Ig) heavy chain‐genes were in germline configuration. The neoplastic cells were found to react with the monoclonal antibody RAB‐1 — originally described as belonging to the B lineage‐restricted monoclonal antibodies — and to carry RAB‐1/CD‐8 in a double marker assay. Natural killer activity of PBMNCs against K562 target cells was severely reduced, while the cells were found to exert strong antibody‐dependent cellular cytotoxicity.