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M J Bosma

Publications and source records attributed to M J Bosma.

At least 37 records · Page 2Linked to original sources
PubMed1991

The SCID mouse mutant: definition, characterization, and potential uses.

Mice homozygous for the scid mutation (scid mice) are severely deficient in functional B and T lymphocytes. The mutation appears to impair the recombination of antigen receptor genes and thereby causes an arrest in the early development of B and T lineage-committed cells; other hematopoietic cell types appear to develop and function normally. The arrest in lymphocyte development is not absolute; some young adult scid mice are "leaky" and generate a few clones of functional B and T cells. By 10-14 months of age, virtually all scid mice are leaky. Scid mice readily support normal lymphocyte differentiation and can be reconstituted with normal lymphocytes from other mice and even partially reconstituted with human lymphocytes. They also support the growth of allogeneic and xenogeneic tumors. Thus, scid mice are of interest for studies of both normal and abnormal lymphocyte development and function. In addition, they can be used to study the function of nonlymphoid cell types in the absence of lymphocytes.

Animals↗
PubMed1990

Defective V-to-J recombination of T cell receptor gamma chain genes in scid mice.

The status of T cell receptor gamma chain genes (TcR gamma) in 11 spontaneous T cell lymphomas from mice with severe combined immune deficiency (scid) was analyzed. We found that as a result of large abnormal deletions accompanying attempted site-specific V-to-J recombinations, 36 of 47 rearranged TcR gamma genes lacked the variable (V) and/or joining (J) region gene segment involved in this attempted recombination. No such deletions were found in T cell lymphomas from normal mice. We interpret our data as indicating a defective V-to-J recombination in scid lymphocytes consistent with our earlier observation of faulty D-to-J recombination in transformed scid lymphocytes (Schuler et al., Cell 1986. 46: 963). The present results further support the hypothesis that the scid mutation affects a component of the VDJ-recombinase system used in common by B and T cells to assemble antigen receptor genes.

Animals↗
PubMed1990

Development of B-lineage cells in the bone marrow of scid/scid mice following the introduction of functionally rearranged immunoglobulin transgenes.

Mice homozygous for the mutation scid (scid mice) are severely immunodeficient and generally lack detectable numbers of pre-B, B, and T cells. This condition is believed to result from a defect in the mechanism responsible for rearrangement of immunoglobulin and T-cell receptor genes in developing B and T lymphocytes. To test this hypothesis and evaluate whether scid affects only the process of gene recombination, we introduced functionally rearranged immunoglobulin genes into the scid mouse genome. As scid mice appear to contain early lymphoid cells committed to the B lineage (pro-B cells), we asked whether the introduction of an IgM heavy-chain gene alone (mu-transgenic scid mice) or both IgM heavy- and kappa light-chain genes (mu kappa-transgenic scid mice) would allow further differentiation of scid pro-B cells into pre-B and B cells. We found that normal numbers of pre-B cells appeared in the bone marrow of mu-transgenic scid mice and that both pre-B and B cells appeared in the bone marrow of mu kappa-transgenic scid mice. However, in the latter case, the number of pre-B and B cells was 2- to 3-fold less than in the controls (mu kappa-transgenic scid heterozygotes) and few, if any, B cells were detectable in the peripheral lymphoid tissues. The implications of these results for the above hypothesis are discussed.

Animals↗
PubMed1990

T-cell receptor gene rearrangements in functional T-cell clones from severe combined immune deficient (scid) mice: reversion of the scid phenotype in individual lymphocyte progenitors.

The severe combined immune deficient (scid) mouse mutant is characterized by a general absence of functional B and T lymphocytes. This deficiency appears to result from a defect in the variable-diversity-joining (VDJ) recombinase system, which is responsible for the assembly of V, D, and J gene segments that code for immunoglobulin and T-cell receptor (TCR) V regions. Most rearranged immunoglobulin or TCR genes in transformed scid lymphocytes contain abnormal J-associated deletions and are nonfunctional. A few functional lymphocyte clones do arise, however, in some young adult scid mice and in virtually all old scid mice; this phenomenon is referred to as leakiness. Alloreactive, CD3+ T-cell clones were isolated from leaky scid mice and the status of their TCR beta and gamma loci was examined in an effort to assess the nature of the recombinase activity that gives rise to functional scid lymphocytes. The recombination junctions of six gamma and two beta alleles were sequenced, representing four alloreactive T-cell clones. All of the junctions were indistinguishable from those seen in normal cells. These results cannot be attributed to selection by antigen because other rearranged TCR genes account for the TCR molecules expressed by these T-cell clones. We conclude that reversion of the scid phenotype can occur in rare lymphocyte progenitors and may account for most functional lymphocyte clones in leaky scid mice.

Animals↗
PubMed1989

Occurrence of mature B (IgM+, B220+) and T (CD3+) lymphocytes in scid mice.

Scid mice with and without detectable serum Ig (scid Ig+ and scid Ig- mice, respectively) were examined for the presence of mature "leaky" lymphocytes by flow microfluorimetry with the use of antibodies to B (IgM, B220) and T (CD3, CD4, CD8) lymphocyte surface Ag. The data showed that leaky scid mice are more frequent than is evident from serum Ig analysis and that the incidence of detectable B and T cells increases with age. IgM+ B220+ cells were not detectable in young adult mice (3 mo old), but in old mice (greater than or equal to 1 yr old) they were routinely present in the peritoneal cavity though not in the spleen. Striking differences in the representation of T cell subsets were seen in the thymus of these two age groups. Most young adult mice contained CD3- populations of CD4/CD8 double positive cells, and in some cases, CD4 or CD8 single positive cells as well. By contrast, identifiable T lineage cells in old mice were all CD3+ and predominantly single positive for CD4 or CD8. Detectable peripheral T cell populations numbered less than 10(5) cells, and the representation of T subset markers (CD4, CD8) varied widely among individual mice; further, Southern blot analysis of TCR gene rearrangements in the DNA of polyclonally stimulated lymphoid cultures from these mice showed very restricted heterogeneity relative to that of cultures from normal mice. We conclude that most leaky mice contain very few T cell clones.

Aging↗
PubMed1989

T cell leakiness in scid mice.

FACS analysis showed that the incidence of leaky T cells increases with age, such that virtually all old scid mice (greater than 1 year) contain detectable CD3+ cells. The number of detectable T cells remained very low; individual old scid mice generally contained less than 10(5) CD3+ cells. When CD3+ populations in individual leaky mice were analyzed for expression of the T cell subset markers, CD4 and CD8, the ratios of CD4/CD8 were found to be markedly skewed relative to normal mice. This suggested the presence of very few T cell clones. Indeed, the analysis of TCR gene rearrangements in polyclonally stimulated T cell cultures revealed only 1-5 clones in the pooled spleen and lymph nodes of individual old scid mice. These studies also indicated that TCR gene rearrangements in the majority of the stimulated T cell cultures did not contain abnormal J-associated deletions that are characteristic of antigen receptor genes of scid lymphomas. Four of five alloreactive T cell clones from leaky scid mice also apparently lacked abnormal J-associated deletions in their rearranged TCR alleles. Therefore, most leaky lymphocytes appear to derive from progenitors with normal or near-normal scid recombinase activity. However, one of five leaky T cell clones (S1233) and one Con A stimulated monoclonal culture (8706) contained both normally and abnormally rearranged TCR genes. The configuration of TCR loci in such clones may reflect the ability of the defective scid recombinase to mediate normal rearrangements at a low frequency.

Animals↗
PubMed1988

The defect in murine severe combined immune deficiency: joining of signal sequences but not coding segments in V(D)J recombination.

Pre-B and pre-T cell lines from mutant mice with severe combined immune deficiency (scid mice) were transfected with plasmids that contained recombination signal sequences of antigen receptor gene elements (V, D, and J). Recovered plasmids were tested for possible recombination of signal sequences and/or the adjacent (coding) sequences. Signal ends were joined, but recombination was abnormal in that half of the recombinants had lost nucleotides from one or both signals. Coding ends were not joined at all in either deletional or inversional V(D)J recombination reactions. However, coding ends were able to participate in alternative reactions. The failure of coding joint formation in scid pre-B and pre-T cells appears sufficient to explain the absence of immunoglobulin or T cell receptor production in scid mice.

Animals↗
PubMed1988

Abnormal recombination of Igh D and J gene segments in transformed pre-B cells of scid mice.

Studies of Ig and TCR genes in transformed lymphocytes of scid mice have revealed aberrant DNA rearrangements. Here we present a more detailed analysis of the Igh gene recombination in nine scid pre-B cell lines transformed by Abelson murine leukemia virus. We found 85% of the rearranged Igh alleles to contain abnormal Dh-Jh deletions of varying size. All of these deletions encompassed Jh elements and extended into the Igh enhancer region, occasionally involving the switch (S) region of the C mu gene. Some of these rearrangements removed most of the Dh elements, but none appeared to extend to the Vh genes. DNA sequence analysis of the two abnormally rearranged Igh alleles in one pre-B cell line showed that no Dh or Jh coding sequences were retained at the recombination sites though heptamer-like (CACTGTG) recognition signal sequences were present in the absence of nonamer (GGTTTTTGT) recognition signal sequences. These results imply that a deregulated recombinase activity may be responsible for the abnormal Dh-Jh deletions and the absence of Vh-Dh joining in established lines of Abelson murine leukemia virus-transformed scid pre-B cells.

Animals↗
PubMed1988

Early B-cell precursors in scid mice: normal numbers of cells transformable with Abelson murine leukemia virus (A-MuLV).

scid mice lack detectable B and T lymphocytes; there are no typical pre-B cells as defined by c mu and surface markers in their bone marrow and their thymus contains only 1% of the normal number of cells. In these characters scid mice seem to lack lymphoid stem cells. However, some mice have detectable serum immunoglobulin and others develop thymomas; both observations indicate that the block in lymphoid development is not absolute. To determine whether scid mice have any B-cell precursors, we looked for pre-B cells by their ability to be transformed by Abelson murine leukemia virus (A-MuLV). Surprisingly, scid mice contain as many B-cell precursors transformable with A-MuLV as normal control mice. Cell-surface markers specific for pre-B and B cells were detected on the A-MuLV-transformed bone marrow cells of both scid and normal mice, indicating that the A-MuLV-transformed cells belong to the B lineage. Interestingly, the same surface markers were undetectable on nontransformed scid bone marrow cells. We conclude from these results that scid mice have normal numbers of early B-cell precursors but that their differentiation into functional B cells is severely impaired.

Abelson murine leukemia virus↗
PubMed1988

Evidence of functional lymphocytes in some (leaky) scid mice.

Although the majority of severe combined immune deficiency (scid) mice lack functional lymphocytes, some (2-23%) appear to develop a limited number of B and T cells between 3 and 9 mo old. Most of these leaky scid mice were shown to contain very few clones (less than or equal to 3) of Ig-producing plasmacytes. Clonal progeny were distributed unevenly in the lymphatic tissues and appeared as discrete plasmacytic foci. In many cases, individual clones persisted for several months and produced abnormally high concentrations of Ig that included multiple isotypes. Functional T cells were inferred from the ability of leaky mice to reject allogeneic skin grafts, a T cell-dependent reaction. Interestingly, approximately 40% of leaky mice developed thymic lymphomas. In other respects, leaky mice resembled regular scid mice; e.g., their splenic cells failed to express common lymphocyte antigens (Ly-5[B220], Ly-1) and to proliferate in response to lymphocyte mitogens. Histologically, their lymphoid tissues retained the same general pattern of severe lymphocytic deficiency as scid mice.

Animals↗