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Biomedical subjects

A Grandien

Publications and source records attributed to A Grandien.

31 records · Page 2Linked to original sources
PubMed1993

Suppression of B cell differentiation by ligation of membrane-bound IgM.

Using B cells from the transgenic mouse line B6-Sp6 and control littermates, stimulated by lipopolysaccharide (LPS) under novel culture conditions that provide for the response of all B cells, we show here that specific ligation of the surface IgM molecules always results in inhibition of terminal differentiation and immunoglobulin secretion by activated cells, regardless of the ligand. Thus, monoclonal antibodies to (a) the CH region of Ig (anti-mu and anti-allotype), (b) the C kappa region, (c) the V region (anti-idiotype) of surface IgM, as well as (d) multivalent antigen (2,4,6-trinitrophenyl-bovine serum albumin), all show similar effects and dose-response curves. IgD-negative transgenic B cells are equally sensitive to IgM ligation-dependent inhibition, as control (IgD-positive) B cells. The allotype specificity of this inhibition, assessed by using anti-mu allotype reagents to inhibit and assay the responses, suggests that B cells expressing transgenic or endogenous IgM in transgenic B6-Sp6 mice are largely independent populations. These observations establish that anti-IgM antibodies in conjunction with appropriate LPS stimulation, provide a universal model system for functional characterization of B cell responses.

Animals↗
PubMed1993

Evidence for selective pressure in the appearance of monoclonal immunoglobulins during aging: studies in M54 mu-transgenic mice.

Serum monoclonal immunoglobulins (M-Ig) appear during aging but little is known about the immunological factors which lead to their development. We have investigated whether such M-Ig occur as a clonally random process or result from V-region-directed selective pressures. We have analyzed a mu-transgenic mouse strain in which over 95% of all splenic B cells express the transgenic mu chain. All endogenous repertoire and mu-chain diversity are generated from the 5% of the B cells which express endogenous mu chains. Not one of the M-Ig detected in these mice were of transgene origin alone; 11 of the 14 M-Ig did not express a mu chain and none of the mu chain containing M-Ig expressed the transgene allotype alone. This observation suggests that the B cells giving rise to M-Ig are heavily selected from among the small number of B cells which express endogenous Ig. The selective factors that might act on the endogenous B cell pools are discussed.

Aging↗
PubMed1993

Global analysis of antibody repertoires. II. Evidence for specificity, self-selection and the immunological "homunculus" of antibodies in normal serum.

The serum IgM repertoires of C57BL/6, DBA/2 and BALB/c mouse strains were analyzed using a recently developed global and quantitative assay that measures antibody reactivities to a very large number of antigens. A characteristic repertoire could be assigned to each strain. The different repertoires could be successfully classified with multivariate statistics. Many common reactivities were also observed among the different strains, which allows the definition of a mouse-specific repertoire. Analysis of human sera support this notion. To investigate the impact of minor genetic differences on the serum IgM repertoire, the congenic strains B10.D2/oSn and B10.D2/nSn, which differ in the expression of the C5 component of complement, were analyzed. The two strains could be separated based on the reactivity profiles obtained. The analysis of the results reveals that many antigenic proteins are not recognized at all by natural antibodies, while others are disproportionately reactive, the resulting patterns giving rise to what could be the definition of an "immunological homunculus". The relevance of this type of analysis for clinical applications is discussed.

Adult↗
PubMed1993

Development of B cells secreting endogenous or transgene-encoded immunoglobulins in H-chain transgenic mice.

The development of splenic B cells secreting transgene-encoded or endogenous immunoglobulin (Ig) was analysed in the mu heavy (H-)chain transgenic mouse line M54. The results show that cells secreting endogenous Ig are not detectable during the perinatal period, even after lipopolysaccharide stimulation in vitro. At this time, transgene-secreting cells are readily detectable and keep increasing with age of the animals. After a few weeks of age cells secreting endogenous Ig appear in the spleen and keep increasing with age, reaching numbers comparable to non-transgenic littermates by 5 weeks of age. Thereafter, the proportion of transgene-secreting B cells decreases. We conclude that the preferential expression of endogenous Igs by secreting B cells in the adult does not result from peculiar genetic features of those cells, but from age-dependent cellular selection operating on all B cells.

Age Factors↗
PubMed1992

On the origin of natural IgM in immunoglobulin transgenic mice.

Surface transgenic IgM was expressed by > 95% of small resting splenic B cells but only by 50% of CD5+ and CD5- peritoneal B cells from the mu-transgenic mouse line M54. Transgenic male M54 were crossed with female CBA/N mice carrying the Xid defect. Offspring F1 animals carrying the transgene were analysed for the presence of transgenic and endogenous IgM expressed both in the serum as well as on the surface of splenic and peritoneal B cells. We found that the levels of serum IgM coded for by the transgene were similar in both F1 male, which lack CD5 B cells, and female transgenic mice, which have CD5 B cells. Thus, the Xid defect does not influence the expression of the transgene at the level of naturally activated plasma cells, a finding substantiated by the fact that both male and female naturally activated splenic plasma cells express the transgene at the same frequency. F1 hybrid mice, like transgenic C57BI/6 M54 mice, have naturally activated splenic plasma cells that overexpress endogenous IgM coded for by the VH gene family Q52. The data indicate that normal serum IgM is not derived from CD5+ B cells and that the serum IgM coded for by the mu-transgene from M54 is produced at normal levels even in the male F1 mouse which lacks CD5+ B cells.

Animals↗
PubMed1991

Endogenous VH gene family expression in immunoglobulin-transgenic mice: evidence for selection of antibody repertoires.

VH gene family expression in single cells of the emergent, available and actual B cell repertoires of C57BL/6 mice was compared to that of two immunoglobulin (Ig)-transgenic B6 lines (B6-Sp6 and M54). We found that less than 5% of bone marrow cells of transgenic mice express endogenous VH genes and that the vast majority (95%) of the peripheral, mature B cell repertoire in these animals is composed of cells expressing the VHJ558 transgenic family. Unimmunized transgenic mice, however, diversify VH gene family usage by 'background' Ig-secreting cells in the spleen, greater than 50% of which express endogenous VH genes. The pattern of endogenous VH gene family expression in the actual repertoire of B6-Sp6 mice is indistinguishable from that of normal B6 mice. In contrast, actual repertoires of M54 mice differ by a 4- to 5-fold higher representation of the VHQ52 family. These results demonstrate a powerful positive selection of B cells into the secretory compartments of unimmunized animals, show that actual and available repertoires differ very markedly, and suggest that V region interactions participate in the selection of 'natural antibody' repertoires.

Animals↗
PubMed1990

Selective peripheral expansion and activation of B cells expressing endogenous immunoglobulin in mu-transgenic mice.

Two different lines of C57BL/6 mice (IgHb) carrying complete rearranged mu chain genes from BALB/c (IgMa) were analyzed for the expression and secretion of endogenous as well as transgenic immunoglobulins at the level of single cells. Quantitation of B cells expressing endogenous IgMb by cytofluorometry, limiting dilution analyses of clonal precursors and secretory cell assays revealed a marked selective expansion, activation and terminal differentiation of those cells producing endogenous immunoglobulins. Thus, the very infrequent IgMb-bearing B cells produced in bone marrow of transgenic mice accumulate in spleen, where they are activated and account for roughly half of all natural immunoglobulin-secreting cells. These observations indicate that mu-transgenic mice are valuable in studies of the antibody repertoire selection operating in unprimed animals but their use could be misleading in the analyzing "monoclonal" immune system.

Animals↗
PubMedDate not supplied

Characterization of the human FLICE-inhibitory protein locus and comparison of the anti-apoptotic activity of four different flip isoforms.

Death receptor-mediated apoptosis is involved in the regulation of immune responses and in the maintenance of immunological tolerance. FLICE-inhibitory proteins (FLIPs) are important modulators of death receptor-mediated apoptosis. To date, the FLIP family encompasses multiple members, of which some are reported to be antiapoptotic and others pro-apoptotic. This led us to investigate the activity of several FLIP proteins in vitro. Concomitant with the cloning of various FLIP isoforms, a new and unexpected member of the FLIP family, denoted FLIPR, was isolated from the human Burkitt lymphoma B-cell line Raji. During the characterization of FLIPR, the genomic sequence of human FLIP was found in the NCBI GenBank. This enabled us to present the complete exon-intron constellation of the human FLIP gene and the generation of all known human FLIP isoforms by alternative splicing. We show that the human FLIP gene with a size of approximately 48 kb, consists of at least 14 exons and can give rise to 11 distinct isoforms by alternative splicing. When studying the activity of some of these isoforms, including FLIPR, they all efficiently inhibited Fas-mediated apoptosis in A20 B lymphoma cells by impeding caspase-8, -3 and -7 activity as well as poly(ADP-ribose) polymerase (PARP) cleavage.

Amino Acid Sequence↗