Biomedical subjects

S F Ziegler

Publications and source records attributed to S F Ziegler.

59 records · Page 4Linked to original sources

PubMed1984

Long-term cultured B lymphocytes and their precursors reconstitute the B-lymphocyte lineage in vivo.

Long-term in vitro cultured B lymphocytes and their precursors were tested for their ability to reconstitute a functional B-cell lineage in vivo. Continuous in vitro production of cells representing early stages of the B-lymphocyte lineage originates from a bone marrow cell type that can be distinguished from a multipotential hematopoietic stem cell. Progenitors of the long-term cultured B-lymphoid cells are recoverable in vitro after in vivo passage into lethally irradiated mice. Long-term cultured B-lymphoid cells and their progenitors reconstituted the B-lymphocyte lineage and restored normal humoral immunity in genetically defective mice. Cultured B-lymphoid cells did not cause lymphoid tumors in vivo in irradiated syngeneic mice. These findings indicate that multipotential hematopoietic stem cells are not directly required for the continued production of functionally competent B lymphocytes in vitro, and they suggest the existence of a B lymphoid progenitor cell with in vitro, and possibly in vivo, stem cell-like qualities.

Animals↗

PubMed1984

kappa gene diversity among the clonal progeny of pre-B lymphocytes.

Some clonal pre-B cell lines, when transformed by Abelson murine leukemia virus, are able to rearrange and express kappa light chain genes. We have analyzed the light chains expressed in sets of early B-cell subclones derived from two pre-B cell clones. Each subclone makes an indistinguishable mu heavy chain, while the kappa gene rearrangements and proteins synthesized were distinct. All members of one set of subclones expressed a V kappa 21 kappa light chain. Only one of the members of the other two sets of subclones expressed V kappa 21. Thus, a single pre-B-cell clone can select a kappa variable region from more than one family. In each subclone of the set that expressed V kappa 21 light chain the same member appears to be used. The differences detected in the expressed proteins can best be explained by primary sequence alterations in the rearranged V kappa 21 segment. These sequence alterations have resulted in a restriction site polymorphism in the expressed V kappa 21 gene and charge and size differences in the expressed proteins. These data suggest that diversification of kappa light chains can occur at the pre-B- to early B-cell stage of development.

Abelson murine leukemia virus↗

PubMed1983

Differentiation of cloned populations of immature B cells after transformation with Abelson murine leukemia virus.

The nature of the target cell for Abelson virus transformation and the effect of transformation on B cell differentiation were studied with six cloned lines of nontransformed immature B lymphocytes. Three clones were at the pre-B cell stage of maturation prior to A-MuLV infection; two were at the B cell stage, and one appeared to represent a stage prior to rearrangement of the mu heavy chain gene. All six cloned lines could be transformed by Abelson virus. Many of the transformants of the pre-B cell clones underwent kappa light chain gene rearrangement and expression following viral infection. Distinct light chain gene rearrangements were segregated by further subcloning these transformed lines. Abelson virus infection of one cloned cell line believed to represent a stage of maturation prior to the pre-B cell stage produced pre-B cell transformants with a variety of heavy chain gene rearrangements. Thus B lymphoid target cells for Abelson virus are not restricted to a single developmental stage, and some transformed subclones can undergo extensive immunoglobulin gene rearrangements shortly after viral infection.

Abelson murine leukemia virus↗

PubMed1983

Progression of the transformed phenotype in clonal lines of Abelson virus-infected lymphocytes.

Some molecular changes which correlate with the tumorigenic progression of neoplastic cells can best be studied with in vitro cell lines that represent each stage in the progression. Lymphoid cells infected by Abelson murine leukemia virus exhibit a wide range of growth potential in vitro and in vivo. Uncloned populations that are poorly oncogenic early after infection become progressively more oncogenic with successive passages of the cells in culture. In such mass cultures, it is difficult to evaluate whether a rare subpopulation of highly oncogenic cells becomes dominant in the culture or whether the individual cells progress in oncogenic phenotype. To examine this latter possibility, Abelson virus-infected lymphoid cells were cloned by limiting-dilution culture 10 days postinfection. We isolated two clones that grew poorly in agar, required feeder layers of adherent bone marrow cells for growth in liquid culture, and were extremely slow to form tumors in syngeneic animals. Both clones, after passage in the presence of adherent feeder layers for 3 months, grew well in liquid and agar-containing cultures in the absence of feeder layers and formed tumors in animals at a rapid rate. The progression of these clonal cell lines to a more malignant growth phenotype occurred in the absence of detectable changes in the concentration, half-life, phosphorylation, in vitro kinase activity, or cell localization of the Abelson virus-encoded transforming protein. No change in the concentration or arrangement of integrated Abelson viral DNA sequences was detected in either clone. Thus, perhaps changes in the expression of cellular genes would appear to alter the growth properties of lymphoid cells after their initial transformation by Abelson virus. Such cellular changes could complement the activity of the Abelson virus transforming protein in producing the fully malignant growth phenotype.

Abelson murine leukemia virus↗

PubMed1981

Lethal effect of the Abelson murine leukemia virus transforming gene product.

Infection of NIH/3T3 and Balb/c/3T3 fibroblastic cell lines by Abelson virus results in stable transformation in most cases. We have observed that certain rodent cell lines, including some Balb/c/3T3 sublines, do not maintain stable transformation following infection. Within three to four weeks of infection of these cell lines a large fraction of the cells is not recoverable upon serial passage and appear to be killed. The residual population of cells displays a flat, nontransformed phenotype. Concomitant with this reversion is the loss of the integrated provirus and loss of expression of the Abelson virus transforming protein. This loss of the integrated provirus is specific to transformation-competent viral strains. The effect of Abelson virus on these cells appears to be, in part, due to a lethal effect of the transforming protein on the cells. We have selectively isolated mutants of Abelson virus that stably transform these rodent cell lines without expressing a lethal effect. Analysis of the nucleic acid and protein structure of these mutant virus strains showed that the transforming proteins are shorter, having lost expression of the carboxy-terminal one third of the protein. We suspect that the carboxy-terminal portion of the wild-type Abelson protein may modulate the in vivo expression of the protein kinase activity and that this may cause the transforming protein to have a deleterious effect on certain cell lines.

3T3 Cells↗