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M W Retter

Publications and source records attributed to M W Retter.

8 recordsLinked to original sources
PubMed1999

Receptor editing: genetic reprogramming of autoreactive lymphocytes.

The clonal selection theory postulates that immune tolerance mediated selection occurs at the level of the cell. The receptor editing model, instead, suggests that selection occurs at the level of the B-cell receptor, so that self-reactive receptors that encounter autoantigen in the bone marrow are altered through secondary rearrangement. Recent studies in transgenic model systems and normal B cells, both in vivo and in vitro, have demonstrated that receptor editing is a major mechanism for inducing B-cell tolerance.

Alleles↗
PubMed1998

Receptor editing occurs frequently during normal B cell development.

Allelic exclusion is established in development through a feedback mechanism in which the assembled immunoglobulin (Ig) suppresses further V(D)J rearrangement. But Ig expression sometimes fails to prevent further rearrangement. In autoantibody transgenic mice, reactivity of immature B cells with autoantigen can induce receptor editing, in which allelic exclusion is transiently prevented or reversed through nested light chain gene rearrangement, often resulting in altered B cell receptor specificity. To determine the extent of receptor editing in a normal, non-Ig transgenic immune system, we took advantage of the fact that lambda light chain genes usually rearrange after kappa genes. This allowed us to analyze kappa loci in IgMlambda+ cells to determine how frequently in-frame kappa genes fail to suppress lambda gene rearrangements. To do this, we analyzed recombined VkappaJkappa genes inactivated by subsequent recombining sequence (RS) rearrangement. RS rearrangements delete portions of the kappa locus by a V(D)J recombinase-dependent mechanism, suggesting that they play a role in receptor editing. We show that RS recombination is frequently induced by, and inactivates, functionally rearranged kappa loci, as nearly half (47%) of the RS-inactivated VkappaJkappa joins were in-frame. These findings suggest that receptor editing occurs at a surprisingly high frequency in normal B cells.

Amino Acid Sequence↗
PubMed1998

Autoreactive B cell regulation: peripheral induction of developmental arrest by lupus-associated autoantigens.

Anti-Sm and anti-ssDNA transgenic (Tg) mice were generated using the VH-D-JH rearrangement of an anti-Sm hybridoma of MRL/Mp-lpr/lpr origin. B cells of each specificity account for 15%-35% of the splenic repertoire, but no circulating anti-Sm or anti-ssDNA antibodies are detected. Most autoreactive cells exhibit an immature B cell phenotype and have short half-lives equivalent to those of non-Tg immature B cells. However, at least some anti-Sm B cells are functional, because immunization with murine snRNPs induces anti-Sm secretion. We propose that anti-Sm and anti-ssDNA are eliminated during the transition to mature B cells and that this late stage of tolerance induction is consequential to their spontaneous activation in murine lupus.

Animals↗
PubMed1996

Both Sm and DNA are selecting antigens in the anti-Sm B cell response in autoimmune MRL/lpr mice.

More than half of the anti-Sm hybridomas isolated from MRL/Mp-lpr/lpr (MRL/lpr) mice produce Abs that also bind ssDNA, and half of these bind dsDNA. Intraclonal comparisons indicate that DNA is a selecting Ag for at least some dual-binding clones. To determine whether Sm itself is a selecting Ag for anti-Sm, we have identified the somatic mutations within the expressed VH and V kappa genes of eight anti-Sm hybridomas, six of which do not bind DNA. We find these V genes have between 0 and 12 somatic mutations each, and that four hybridomas possess a higher number of heavy or light chain CDR replacement (R) mutations than expected by chance, suggesting that these anti-Sm-producing B cells have undergone Ag selection. To demonstrate directly the effect of somatic mutation on Sm binding, we have engineered the unmutated counterpart of Ab 2-12, an Sm-specific hybridoma Ab with a nonrandom distribution of V kappa CDR R mutations, and compared its ability to bind Sm and ssDNA with that of the originally isolated 2-12 Ab. We find that the unmutated Ab has a much lower avidity for Sm than the mutant, but, unlike the mutant, it binds ssDNA. We conclude that Sm can drive clonal expansion in the anti-Sm response, and that Sm-only binding B cells can arise from Sm/DNA dual-binding B cell clonal precursors. These data also suggest that dual binding is not necessary to sustain clonal expansion. Thus, this response is unique in that it can be driven by either of two Ags.

Amino Acid Sequence↗
PubMed1995

Sm and DNA binding by dual reactive B cells requires distinct VH, V kappa, and VH CDR3 structures.

We have previously demonstrated an overlap of the anti-Sm and anti-DNA responses in MRL/Mp-lpr/lpr mice. The Ab produced by many anti-Sm hybridomas bind DNA and are encoded by Ig V genes used by anti-DNA hybridomas. In addition, some anti-Sm Ab that bind DNA have acquired mutations that improve DNA binding, indicating that DNA is a selecting Ag in the anti-Sm response. To gain insight into the basis for the dual binding ability of these Ab, we coexpressed the H chain from the anti-Sm hybridoma 2-12 with nine different L chains. Hybridoma 2-12 binds Sm but not DNA, yet expresses the same J558 VH gene as three anti-Sm hybridomas that bind ssDNA and at least one anti-DNA hybridoma that does not bind Sm. We found that most of the transfectoma Ab bind Sm, but their avidities vary over more than 3 orders of magnitude. Five of the nine transfectoma Ab bind ssDNA, and none bind dsDNA. In general, the ability to bind each Ag follows the binding ability of the hybridoma from which the L chain is derived. H Chain swapping experiments indicate that the H chain, VH CDR3 in particular, contributes to the binding of both Sm and DNA. We conclude that Sm and DNA select for distinct features of VH, V kappa, and VH CDR3, suggesting selection by both Ag in the anti-Sm response.

Amino Acid Sequence↗
PubMed1993

V region gene analysis of anti-Sm hybridomas from MRL/Mp-lpr/lpr mice.

Anti-Sm autoantibodies are unique to SLE, but are present in only 25% of patients with this disease. This response also occurs at a similar frequency in mice of the autoimmune MRL strains. Previous analyses of the anti-Sm response in these mice indicate that its occurrence is controlled by stochastic events, and suggest that Sm is the driving Ag. To further elucidate the role of Ag in this response, and to test the hypothesis that the 25% incidence is due to a requirement for particular Ig gene rearrangements or somatic mutations, we have analyzed the specificity and V-region gene sequences of 41 anti-Sm B cell hybridomas derived from nine anti-Sm-positive MRL/Mp-lpr/lpr mice. The majority of hybridomas are specific for the D peptide of the Sm particle. Hybridomas of independent origin express unique VH/V kappa combinations with diverse junctional sequences and are variable in the extent of somatic mutation. Thus, the response does not appear to be dependent upon the occurrence of a rare Ig gene rearrangement or specific somatic mutation. The response exhibits restriction in JH and VH gene use, and in individual mice is oligoclonal, suggestive of Ag selection. In the few B cells for which mutations can be identified, the evidence for selection of mutant B lymphocytes, based on patterns of mutation, is ambiguous. However, there is remarkably little intraclonal diversity, suggesting that the overall mutation rates in these clones are low.

Amino Acid Sequence↗
PubMedDate not supplied

Detection of mammaglobin in the sera of patients with breast cancer.

Current procedures for the diagnosis of breast cancer are cumbersome and invasive, making detection of this disease difficult. A rapid screening test for early detection of breast cancer would allow for better management of this deadly disease. In this report, we show that, with the exception of the skin, mammaglobin mRNA is specifically expressed in mammary tissue and commonly overexpressed in breast cancer. Mammaglobin is not expressed in other types of cancer including colon, lung, ovarian, and prostate cancer. Breast-specific expression of mammaglobin protein was shown using immunohistochemical methods. Mammaglobin is secreted from both established breast cancer cell lines and primary breast carcinoma cells cultured in vitro. Using a monoclonal antibody-based assay for monitoring the presence of mammaglobin in serum, elevated levels of mammaglobin were detected in sera of patients with breast cancer, but not in healthy women. Thus, mammaglobin, which is overexpressed and secreted from breast carcinoma cells, is detectable in sera of patients with breast cancer and may provide a rapid screening test for the diagnosis and management of breast cancer.

Adult↗