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J J Cebra

Publications and source records attributed to J J Cebra.

At least 91 records · Page 5Linked to original sources
PubMed1981

Rise in inulin-sensitive B cells during ontogeny can be prematurely stimulated by thymus-dependent and thymus-independent antigens.

We have shown that the delayed acquisition of competence in expression of an anti-inulin (IN) response by neonatal BALB/c mice is preceded by a natural increase in the frequency of IN-sensitive B cells between 3 to 5 weeks of life. Up until 3 weeks of age, BALB/c mice resemble adult germfree mice in their low frequency of IN-sensitive B cells (1 to 2/10(6) B cells). Thereafter, the population of IN-reactive B cells rises about 10-fold to the young adult level, without deliberate immunization. This naturally expanded population of IN-reactive cells has an isotype profile resembling populations arising after intentional priming with other antigens in that it contained a large proportion of cells which generated clones expressing immunoglobulin G and immunoglobulin A isotypes, often without detectable immunoglobulin M. The late rise in frequency of IN-sensitive precursors could be induced prematurely by deliberate priming at 3 days of age with either the thymus-dependent antigen IN-hemocyanin or the thymus-independent bacterial levan. However, no circulating anti-IN could be detected following this early administration of antigen. Thus, the delayed expression of anti-IN does not reflect an absence of B cells of the appropriate specificity which can be stimulated to divide by antigen but rather other events occurring subsequent to perinatal generation of antigen-sensitive cells. Our observations support a role for the beta2 --> 1 fructosyl group as an environmental determinant which selectively expands out preexisting antigen-sensitive B cells at 3 to 5 weeks of age and these include clonotypes which express the predominant anti-IN idiotypes.

Animals↗
PubMed1981

Most B cells that have switched surface immunoglobulin isotypes generate clones of cells that do not secrete IgM.

The order of genes coding for the constant regions of immunoglobulin heavy chains is 5'-C mu, C delta, C gamma 3, C gamma 1, C gamma 2b, C gamma 2a, C epsilon, C alpha-3'. To try to determine whether switching of the expression of heavy chain genes is irreversible and occurs in a direction from 5' to 3' within a cell line, we have isolated B cells bearing particular membrane isotypes, stimulated them to generate clones, and assayed daughter cells for secreted antibody. B cell with and without surface IgM and IgD, and B cells with and without surface IgG, were isolated by fluorescence-activated cell sorting. Fractionated cells were individually stimulated with phosphorylcholine in a splenic fragment assay, and the antibody secreted by clonal progeny was assayed for several heavy chain isotypes by radioimmunoassay. The results show that 1) B cells bearing IgM and IgD can produce individual clones of cells secreting 3 isotypes of anti-phosphorylcholine antibody--IgM, IgG, and IgA; 2) most B cells expressing surface IgG generate clones that secrete IgG but not IgM; and 3) most B cells from gut-associated lymphoid tissue that do not express surface IgM or IgD generate clones of cells that secrete IgA but not IgM. Therefore, IgM- and IgD-bearing cells can give rise to progeny that secrete IgM, IgG, and IgA. Once B cells switch to a different surface isotype, they appear restricted in isotype potential, since they frequently generate clones of cells that do not secrete IgM. These findings suggest that isotype switching is generally irreversible, and isotypes are expressed in a 5'- to -3' direction that is consistent with the germline gene order.

Animals↗
PubMed1980

Transport of immunoglobulins from serum into colostrum.

Oligomeric, J-chain-containing immunoglobulins were observed to be transferred selectively from serum into colostrum. These studies suggest that, in the case of the mammary gland secretion, a significant role for extraglandular synthesis of IgA merits consideration. Thus, for example, colostrum may contain antibodies synthesized locally as well as antibodies synthesized in the much larger lymphoid tissues such as the gut lamina propria.

Animals↗
PubMed1980

CH gene rearrangements in IgM-bearing B cells and in the normal splenic DNA component of hybridomas making different isotypes of antibody.

To probe mechanisms operating at the CH gene locus during normal B lymphocyte differentiation, we have used cloned probes for the constant region genes Cmu, C gamma 1 and C alpha to analyze the immunoglobulin heavy chain genes of three kinds of cell populations in successive stages of B cell development. These are IGM-bearing B lymphocytes from the normal spleen of unprimed mice, hybridomas prepared by fusing spleen cells from antigen-primed mice with the SP2/O permanent cell line and selected to secrete one of five different isotypes (IgM, IgG3, IgG1, IgG2 and IgA) and a set of plasmacytoma lines. The IgM-bearing B cells carry Cmu genes with rearrangements between VH and JH genes on both chromosomes even though only one chromosome is expressed; clearly, allelic exclusion cannot be explained by the lack of CH gene rearrangement on the nonexpressed chromosome. The normal splenic DNA component of antibody-secreting hybridomas displays rearrangements between JH and Cmu genes as well as among CH genes other than Cmu, with concomitant deletion of CH genes 5' to those expressed. These CH rearrangements and deletions are likely to accompany the isotype switching process and may occur on both expressed and nonexpressed chromosomes. We used hybridomas (spleen-derived), which secrete primarily IgM, and plasmacytomas (gut-derived), which secrete primarily IgA, to represent plasma cells in early and late stages of differentiation, respectively. A direct comparison of hybridomas and plasmacytomas making the same products (IgG3 or IgG1) indicates that hybridomas display a low frequency (2/12) of nonexpressed C alpha gene rearrangements in contrast to the high frequency (7/10) displayed by plasma-cytomas. We propose that CH gene switching rearrangements and deletions may occur successively along the CH gene locus, involving any of the undeleted genes at each step. These can occur on both expressed and nonexpressed chromosomes during the normal clonal outgrowth of a B cell line in vivo, and would result in the accumulation of both productive and nonproductive rearrangements of the presumed last CH gene, C alpha.

B-Lymphocytes↗
PubMed1980

Successive switching of antibody isotypes expressed within the lines of a B-cell clone.

An antigen-stimulated B cell can differentiate to form a clone of cells that secrete antibodies with the IgM, IgG1, and IgA isotypes. We have examined the sequence of isotype expression by proliferating cell lines within a clone by directly staining for immunoglobulin in the cytoplasm of clonal daughter cells. All of the cones selected for analysis originally secreted IgM as well as other isotypes, as determined by radioimmunoassay of culture fluids. Cell staining showed that (i) at least 25% of the cells contained more than one isotype, indicating that cells can switch expression of isotypes during clonal expansion; (ii) some cells contained both IgM and IgA without detectable IgG1, and some cells contained both IgM and IgG1 without detectable IgA, suggesting that cells can switch from IgM directly to IgG1 or IgA; and (iii) some cells contained both IgG1 and IgA, indicating that cell lines can undergo two successive switches from IgM to the IgG1 and IgA isotypes. Using serological markers for allotypic determinants on the constant region of heavy chains, we have also shown that heterozygous B cells specific for phosphorylcholine generated clones of cells that secreted IgG1 and IgA antibodies that were derived from the expression of genes on only one parental chromosome. Assuming that the gene coding for the IgA isotype is the last gene in the gene cluster coding for heavy chain isotypes, we have proposed a model of successive, but not necessarily stepwise, switching of isotypes within B-cell lines, leading to the eventual accumulation of cells expressing IgA.

Animals↗
PubMed1979

Differentiated B lymphocytes. Potential to express particular antibody variable and constant regions depends on site of lymphoid tissue and antigen load.

B cells have the potential to respond to an antigen by producing antibodies with a variety of variable and constant regions. We have quantitatively analyzed B-cell potential at the single cell level to determine the effect of lymphoid tissue site and antigen load on the expression of variable and constant regions. Concerning variable region expression, although the total frequency of B-cell precursors for phosphorylcholine is similar between nonimmune spleen and gut-associated Peyer's patch tissues, the proportion of cells producing non-TEPC 15 idiotypes is greater from Peyer's patch than from spleen. Oral immunization with phosphorylcholine-containing Ascaris suum increased the frequency of non-TEPC 15 B cells. Thus variation in the proportion of cells bearing different variable regions may be related to the distinct antigenic environment of cells in Peyer's patches compared to that of cells in spleen. Regarding constant region expression, although B cells from both spleen and Peyer's patches generate clones producing IgM, IgGl, and IgA singly and in all combinations, cells from Peyer's patches generate more clones secreting only IgA than cells from spleen. B cells specific for phosphorylcholine and inulin, which are found on intestinal bacteria, produce more IgA-only clones than B cells specific for the dinitrophenyl determinant. This striking correlation between IgA expression and variable region specificity for antigen implies that environmental antigens have expanded certain B cells in Peyer's patches which then have the ability to generate progeny that express only IgA. Evidence supporting the secondary nature of precursors for IgA-only clones is obtained by their ability to produce this isotype after stimulation with histoincompatible T cells. The role of gut antigens may be to clonally expand IgA precursors and perhaps to stimulate the proliferation of less differentiated cells within the unique microenvironment of the Peyer's patches, allowing them to differentiate to IgA precursors.

Animals↗
PubMed1979

Isolation and characterization of actin and myosin from B-lymphocytic guinea pig leukemia cells.

Actin and myosin have been isolated from a guinea pig B cell leukemia line, L2C. The m.w. and amino acid compositions of these proteins are similar to actin and myosin from other nonmuscle cell types. L2C actin polymerizes to form filaments and activates the ATPase activity of skeletal muscle myosin. Actin in crude lymphocyte extracts does not polymerize as well as predicted from the critical concentration of purified lymphocyte actin suggesting that other factors in lymphocyte extracts regulate actin polymerization. Lymphocyte myosin polymerizes to form synthetic filaments at low ionic strength. Lymphocyte myosin binds to actin, but its ATPase activity is not activated by actin. Possible mechanisms for regulation of the lymphocyte contractile apparatus and its importance in a number of lymphocyte functions are discussed.

Actins↗
PubMed1978

Guinea pig immunoglobulin light chain isotypes. I. Separation of kappa and lambda chains and the identification of three isotypes of the lambda chain constant homology region.

The separation of intact kappa chain and two fragments comprising lambda (lambda) chain from immunoglobulin light chain pools isolated from strain 13 guinea pigs is achieved by cyanogen bromide digestion and gel filtration before and after reductive clevage of disulfide bonds. The smaller lambda chain fragment derives from the original carboxyl-terminus of lambda chain. The partial sequence of component tryptic and thermolytic peptides of this thirty-nine residue fragment allowed its complete sequence to be deduced. Three isotypic forms of this lambda chain constant region fragment, distinguished by four residue positions showing alternative amino acids, are found expressed by guinea pigs. Each of these three isotypes is more homologous to the other two than to lambda chains of any other species. The distribution of amino acid substitutions differentiating these isotypes further supports the view that lambda chain isotypes arose in guinea pigs, and in several other species, independently by gene duplication.

Amino Acids↗
PubMed1978

Guinea pig immunoglobulin light chain isotypes. II. The preferential expression of lambda chain-bearing anti-phenyltrimethylammonium antibodies is associated with restricted variable region expression, but not with any alteration in the proportion of lambda chain constant region isotypes, relative to normal immunoglobulins.

The inbred strain 13 guinea pig expresses at least three isotypes of immunoglobulin (Ig) lambda chain. The proportion of these isotypes in normal Ig can be estimated by isolating a constant (C) region cyanogen bromide peptide from lambda chains and quantitatively analyzing its component tryptic peptides. Anti-phenyltrimethylammonium antibody, when analyzed in this way, was found to contain the same proportion of each lambda chain C region isotype as did normal Ig. The specific antibody light (L) chain pools were found to contain predominantly lambda chains, although these are the minority type in guinea pig normal Ig L chain pools. Moreover, amino-terminal, 5-pyrrolidone-2-carboxylic acid-containing peptides isolated from antibody lambda chains show no demonstrable sequence heterogeneity, while their homologs isolated from normal lambda chains are markedly heterogeneous. That a restriction in heterogeneity of variable region framework residue positions is not associated with any alteration in the proportion of C region isotypes in these antibody lambda chains, implies that translocation of all guinea pig lambda chain variable region genes to the isotypic C region genes occurs in a random way.

Animals↗