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L Jerabek

Publications and source records attributed to L Jerabek.

18 recordsLinked to original sources
PubMed2001

Molecular cloning and characterization of a novel regulator of G-protein signaling from mouse hematopoietic stem cells.

A novel regulator of G-protein signaling (RGS) has been isolated from a highly purified population of mouse long-term hematopoietic stem cells, and designated RGS18. It has 234 amino acids consisting of a central RGS box and short divergent NH(2) and COOH termini. The calculated molecular weight of RGS18 is 27,610 and the isoelectric point is 8.63. Mouse RGS18 is expressed from a single gene and shows tissue specific distribution. It is most highly expressed in bone marrow followed by fetal liver, spleen, and then lung. In bone marrow, RGS18 level is highest in long-term and short-term hematopoietic stem cells, and is decreased as they differentiate into more committed multiple progenitors. The human RGS18 ortholog has a tissue-specific expression pattern similar to that of mouse RGS18. Purified RGS18 interacts with the alpha subunit of both G(i) and G(q) subfamilies. The results of in vitro GTPase single-turnover assays using Galpha(i) indicated that RGS18 accelerates the intrinsic GTPase activity of Galpha(i). Transient overexpression of RGS18 attenuated inositol phosphates production via angiotensin receptor and transcriptional activation through cAMP-responsive element via M1 muscarinic receptor. This suggests RGS18 can act on G(q)-mediated signaling pathways in vivo.

Amino Acid Sequence↗
PubMed1996

Searching for hematopoietic stem cells. II. The heterogeneity of Thy-1.1(lo)Lin(-/lo)Sca-1+ mouse hematopoietic stem cells separated by counterflow centrifugal elutriation.

Mouse hematopoietic stem cells (HSCs) are highly enriched in the rare (approximately 0.05%) Thy-1.1(lo)Lin(-/lo)Sca-1+ fraction of hematopoietic tissues. It has been demonstrated that Thy-1.1(lo)Lin(-/lo)Sca-1+ cells are the only HSCs in C57BL/Ka-Thy-1.1 bone marrow. In this study, we separated C57/Ka-Thy-1.1 bone marrow cells by counterflow centrifugal elutriation (CCE) into four fractions and characterized Thy-1.1(lo)Lin(-/lo)Sca-1+ cells in each eluted fraction. The peak number of Thy-1.1(lo)Lin(-/lo)Sca-1+ cells was highly enriched in one eluted fraction, which was also highly enriched for day-12 to -13 CFU-S. Activities for day-13 CFU-S, radioprotection, and long-term multilineage reconstitution correlated with, and could be generally predicted by determining, the frequency of Thy-1.1(lo)Lin(-/lo)Sca-1+ cells in a given eluted fraction. However, the fraction that was highly enriched for blast cells and contained a low frequency of Thy-1.1(lo)Lin(-/lo)Sca-1+ cells, only provided short-term but not long-term radioprotection, with a predicted cell number (100 cells) that should have protected > or = 95% (PD95) of hosts. Still, when 300 Thy-1.1(lo)Lin(-/lo)Sca-1+ cells from this fraction (3 X PD95 for unfractionated HSCs) were injected, mice were radioprotected and donor cells provided long-term multilineage reconstitution. We propose that such blast cells may contain two Thy-1.1(lo)Lin(-/lo)Sca-1+ subsets, one providing short-term and the other long-term multilineage sustained hematopoiesis, the latter presumably due to HSC self-renewal.

Animals↗
PubMed1996

Transplantation of purified hematopoietic stem cells: requirements for overcoming the barriers of allogeneic engraftment.

Allogeneic bone marrow transplantation currently plays a critical role in the treatment of leukemias and inherited disorders of hematopoiesis, and it shows great promise for the treatment of numerous other diseases. The problems of graft-vs-host disease (GVHD) and failure to engraft, however, remain formidable obstacles to the widespread use of this therapy. Successful transplantation of purified populations of hematopoietic stem cells (HSCs) can theoretically avoid the problem of GVHD, since purified HSCs lack the mature elements that allow the graft to mount a response against the host. In previous studies from our laboratory, a population of purified HSCs (Thy-1loLin-/loSca-1+) was isolated from mouse bone marrow (BM). These cells represent approximately 0.05% of BM cells and are capable of self-renewal and long-term reconstitution of all blood lineages. Here we report long-term engraftment of these purified HSCs transplanted in mice across successively more difficult allogeneic-histocompatibility barriers. Transplantation of purified HSCs were quantitatively compared with whole bone marrow (WBM) grafts containing equivalent numbers of stem cells. The mouse strain combinations tested were parent transplanted into F1 (Hh disparate), minor histocompatibility complex (mHC), and major histocompatibility complex (MHC) plus mHC disparities. One of the recipient strains studied for MHC-disparate transplantations was that of spontaneously autoimmune diabetic mice. Recipient mice were administered lethal doses of whole-body irradiation in the presence or absence of antibodies directed against natural killer (NK) cell-associated determinants and/or monoclonal antibodies against the CD4+ T cell subset. We find that as the barrier to transplantation increases, greater numbers of HSCs are required for radioprotection and engraftment. In all cases, stable hematopoietic chimeras were generated with HSCs alone, but 10-60 times the number of HSCs was required for radioprotection of mice transplanted across allogeneic or semiallogeneic disparities as compared to Ly-5 congenic differences. Furthermore, we demonstrate a clear advantage of WBM vs HSCs with regard to tha ability to engraft [corrected]. Chimeric mice showed no symptoms of GVHD, and their T cells were unable to induce GVHD in neonatal mice expressing H-2 antigens of donor and host. These data confirm that a cell population resident in WBM and distinct from purified stem cells is important in facilitating hematopoietic engraftment, in this case, of purified allogeneic HSCs. The differences in engraftment between WBM and HSCs could be reduced significantly by the addition of antibodies directed against NK determinants to the host preparative regimen. Similarly, since antibodies directed against host NK-associated antigens can reduce the barrier to allogeneic HSC engraftment, an interaction between the facilitating population within donated WBM and a resistant host population with NK determinants is implied.

Animals↗
PubMed1995

Extrathymic maturation of alpha beta T cells from hemopoietic stem cells.

The object of the study was to determine whether alpha beta T cells can develop from hemopoietic stem cells in the absence of the thymus. C57BL/6 (Ly-5.1 and Thy-1.2) mice were thymectomized or sham-thymectomized at 4 wk of age, and received lethal whole body irradiation 2 wk later. These mice were reconstituted with an i.v. injection of 500 highly purified hemopoietic stem cells (Mac-1-, B220-, TER-119-, CD3-, CD4-, CD8-, Thy 1low, SCA-1+) obtained from the bone marrow of C57BL/6 (Ly-5.2 and Thy-1.1) donors. A similar percentage of Ly-5.2+ alpha beta T cells (donor) was found in the marrow of thymectomized recipients, sham-thymectomized recipients, and normal donor mice at least 3 mo after stem cell transplantation. The percentage of Ly-5.2+ alpha beta T cells in the spleens of sham-thymectomized and normal donor mice was similar. The percentage in the spleens of thymectomized recipients was reduced by about 50%, and approximately one-half of the latter T cells expressed the CD4-CD8- alpha beta+ phenotype. A purified population of Ly-5.2+ alpha beta- cells obtained from the marrow of thymectomized recipients was incubated in vitro for 48 h without exogenous growth factors. After the incubation procedure a proportion of the marrow cells acquired alpha beta TCR surface receptors. The results show that alpha beta T cells can develop from hemopoietic stem cells in the absence of the thymus.

Animals↗
PubMed1994

Rapid and sustained hematopoietic recovery in lethally irradiated mice transplanted with purified Thy-1.1lo Lin-Sca-1+ hematopoietic stem cells.

Hematopoietic stem cells (HSCs) are believed to play a critical role in the sustained repopulation of all blood cells after bone marrow transplantation (BMT). However, understanding the role of HSCs versus other hematopoietic cells in the quantitative reconstitution of various blood cell types has awaited methods to isolate HSCs. A candidate population of mouse HSCs, Thy-1.1lo Lin-Sca-1+ cells, was isolated several years ago and, recently, this population has been shown to be the only population of BM cells that contains HSCs in C57BL/Ka-Thy-1.1 mice. As few as 100 of these cells can radioprotect 95% to 100% of irradiated mice, resulting long-term multilineage reconstitution. In this study, we examined the reconstitution potential of irradiated mice transplanted with purified Thy-1.1lo Lin-Sca-1+ BM cells. Donor-derived peripheral blood (PB) white blood cells were detected as early as day 9 or 10 when 100 to 1,000 Thy-1.1lo Lin-Sca-1+ cells were used, with minor dose-dependent differences. The reappearance of platelets by day 14 and thereafter was also seen at all HSC doses (100 to 1,000 cells), with a slight dose-dependence. All studied HSC doses also allowed RBC levels to recover, although at the 100 cell dose a delay in hematocrit recovery was observed at day 14. When irradiated mice were transplanted with 500 Thy-1.1lo Lin-Sca-1+ cells compared with 1 x 10(6) BM cells (the equivalent amount of cells that contain 500 Thy-1.1lo Lin-Sca-1+ cells as well as progenitor and mature cells), very little difference in the kinetics of recovery of PB, white blood cells, platelets, and hematocrit was observed. Surprisingly, even when 200 Thy1.1lo Lin-Sca-1+ cells were mixed with 4 x 10(5) Sca-1- BM cells in a competitive repopulation assay, most of the early (days 11 and 14) PB myeloid cells were derived from the HSC genotype, indicating the superiority of the Thy-1.1lo Lin-Sca-1+ cells over Sca-1- cells even in the early phases of myeloid reconstitution. Within the Thy-1.1lo Lin-Sca-1+ population, the Rhodamine 123 (Rh123)hi subset dominates in PB myeloid reconstitution at 10 to 14 days, only to be overtaken by the Rh123lo subset at 3 weeks and thereafter. These findings indicate that HSCs can account for the early phase of hematopoietic recovery, as well as sustained hematopoiesis, and raise questions about the role of non-HSC BM populations in the setting of BMT.

Animals↗
PubMed1987

The phenotype of thymocytes derived from a single clonogenic precursor.

Clonogenic repopulation of the thymus of thymus-homing bone marrow cells leads to intrathymic populations representing all four major Lyt-2- and L3T4-defined phenotypes. Although all four phenotypes may be represented in a single clone, quite often a striking bias in the proportion of L3T4 single positive to Lyt-2 single positive cells may exist within a clone, but not in the host thymocytes in general. Because at any one time these clones may be located in specific subregions of the thymus (specifically cortex only, medulla only, or cortex and medulla), we propose the hypothesis that different microenvironments in the thymus might, in fact, be responsible for the predominant maturation of different single positive mature thymic subsets.

Animals↗
PubMed1986

Ontogeny of lymphocyte homing receptor expression in the mouse thymus.

The monoclonal antibody MEL-14 has been used in conjunction with immunohistology and multiparameter immunofluorescence to identify and characterize homing receptor-bearing thymocytes at various stages of embryonic and neonatal development. MEL-14hi thymocytes first appear at day 14 of gestation and come to represent about 40% of day 15 fetal thymocytes. Thereafter, the proportion of MEL-14hi thymocytes rapidly declines such that by birth (usually the 20th day of embryonic development) only about 2% of thymocytes are MEL-14hi. Although newborn thymocytes resemble adult thymocytes in this respect, the phenotypic characteristics of fetal and neonatal MEL-14hi thymocytes suggest that this unique subset undergoes a gradual transition from containing exclusively phenotypically immature cells in early gestation to containing predominantly phenotypically mature cells by young adulthood. Thus, virtually none of day 15 MEL-14hi fetal thymocytes are peanut agglutinin (PNA)lo, Ly-1hi, or either Lyt-2-/L3T4+ or Lyt-2+/L3T4-, whereas in the weeks that follow a steadily greater proportion of MEL-14hi thymocytes come to express this mature pattern (roughly 70% at 4 wk of age). Most day 15 MEL-14hi fetal thymocytes appear to express the functional homing receptor molecule, since day 15 fetal thymocytes bind to peripheral lymph node high endothelial venules about 40 to 50% as well as do adult mesenteric node lymphocytes, whereas adult thymocytes bind only about 5% as well. We have also identified a population of outer cortical MEL-14hi Lyt-2-/L3T4- lymphoblasts that appears during thymus regeneration 5 to 6 days after the administration of hydrocortisone. These lymphoblasts express the same phenotype as cells that constitute 40% of the day 15 fetal thymus and only 0.4% of normal adult thymocytes, implying that this particular subset may make up a significant fraction of thymocytes whenever there is a requirement for rapid expansion of the intrathymic and/or peripheral T cell pools. Taken together, these results are consistent with the notion that expression of the MEL-14-defined homing receptor may be closely linked to important intrathymic events that may occur early in T cell development and yet still have an overriding impact on the selection of those thymocytes that will serve as precursors of thymus emigrants.

Animals↗
PubMed1984

Tolerance and the H-Y antigen: Requirement for male T cells, but not B cells, to induce tolerance in neonatal female mice.

Transplantation tolerance of the H-Y antigen may be induced and transferred by lymphoid cells, but not by nonlymphoid cells. In this study we have demonstrated that amongst lymphoid cells, T cells--but not B cells or macrophages--are capable of inducing transplantation tolerance. In contrast, all three populations express sufficient amounts of immunogenic H-Y antigen to sensitize adult female mice to a subsequent male skin graft, as demonstrated by the second-set reaction.

Animals↗
PubMed1980

T cell maturation: thymocyte and thymus migrant subpopulations defined with monoclonal antibodies to MHC region antigens.

The maturation sequences of thymocytes is known to some extent: A generative layer of subcapsular large lymphoblasts gives rise to a major population of small cortical thymocytes and a minor population of midsize medullary thymocytes. The relative contribution of these three populations to the peripheral T cell populations is not yet known. In this study, subcapsular lymphoblasts, cortical small cells, medullary cells, and thymic emigrant cells have all been analyzed by immunofluorescence for expression of the antigens H-2D, I-A, H-2K, and TL. H-2D is expressed brightly on all subcapsular large cells, dimly on cortical small cells, and brightly on all migrants, cortisone-resistant thymocytes (CRT), and peripheral T cells. I-A can be detected at low levels on 30 to 50% of cells in all the thymic subpopulations, and on 30 to 50% of migrants and peripheral T cells. Fifty to 80% of small cortical cells do not express detectable H-2K, but all the other subpopulations, both inside and outside the thymus, stain uniformly quite brightly. TL3 is expressed on 70 to 80% of subcapsular and cortical thymocytes, 30 to 40% of CRT, is undetectable on migrants but can be seen at low levels on 10 to 20% of spleen and lymph node T cells. The possibility that some or all of these antigens represent stable markers of separate lineages rather than unstable, stage-specific markers is discussed.

Animals↗
PubMed1979

An infectivity assay for bovine leukemia virus using the immunoperoxidase technique.

This report describes the development of a 7-day infectivity assay for bovine leukemia virus (BLV) which is based on the induction of the major internal virion antigen (a protein with a molecular weight of 25,000) in susceptible indicator monolayer cell cultures. In this assay, the antigen is detected in the indicator cells by the immunoperoxidase antibody technique using a specific rabbit antiserum to a BLV protein with a molecular weight of 25,000. The immunoperoxidase infectivity assay is specific, quantitative, reproducible, and more sensitive than the previously described syncytia induction assay. The immunoperoxidase infectivity assay can be applied to the detection of BLV-infected cells and provides a reliable method for the direct diagnosis of BLV infection in cattle.

Animals↗
PubMed1979

A serologic comparison of Moloney lymphoma cell surface and Moloney oncornavirus antigens.

Moloney lymphomas and Moloney sarcomas share strong tumor antigens. In this report we analyze the cell-surface antigens on a Balb/c Moloney lymphoma, LSTRA, using hyperimmune sarcoma regressor sera (alphaMo) as a primary reagent. We also use heterologous anti-viral p30 and gp70 sera for a direct analysis of virion protein antigens on the LSTRA surface. Using radiolabeled alphaMo-binding assays, we demonstrate that LSTRA tumor antigens detected by these sera are all Moloney viral antigens; approximately 1/3 of these antigenic determinants are expressed on the intact virus, and the other determinants are revealed by detergent lysis of the virus. The major viral antigens expressed on the LSTRA cell surface are viral env gene products, whereas gag gene products are only sparsely represented. We conclude that alphaMo sera detect almost exclusively viral antigens on LSTRA cells, and these antigens are almost exclusively virion env gene products.

Animals↗
PubMed1978

An infectivity assay for the bovine leukemia virus based on the induction of the major internal virion antigen in susceptible cell cultures.

This report described the development of a 7-day infectivity assay for the bovine leukemia virus (BLV) which is based on the induction of the major internal virion antigen (p25) in susceptible indicator monolayer cell cultures. In this assay the antigen is detected in the indicator cells by the immunoperoxidase antibody technique using a monospecific anti-BLV serum. The immunoperoxidase infectivity assay (IPIA) is specific, quantitative, reproducible and more sensitive than the previously developed syncytia induction assay. The IPIA can be applied for the detection of BLV-infected cells and provides a reliable method for the direct diagnosis of BLV infection in cattle.

Antigens, Viral↗
PubMedDate not supplied

Mimicking the alloantigenicity of proteins with chemically synthesized peptides differing in single amino acids.

Recent studies have shown that short chemically synthesized peptides very often induce antibodies which react with the cognate sequence in the intact folded protein. Since such antibodies react with known regions of proteins, they are of predetermined specificity and offer a precision not previously possible with immunological probes. A basic concept emerging from the use of such antibodies in viral systems is that the differential immunogenicity of closely related proteins can be mimicked by short peptides which span the regions of sequence variation. To generalize this concept, we have studied the two Thy-1 proteins which vary by only a single amino acid. Chemically synthesized peptides differing in only one out of 19 amino acids were able to induce allospecific antisera. Thus, single amino acid changes have similar effects on the immunogenicity of proteins and small peptides, even though the latter are free from constraints provided by neighbouring structures in the tertiary configuration of the intact folded proteins.

Amino Acid Sequence↗