Regulation of IgM and IgD synthesis in B lymphocytes. I. Changes in biosynthesis of mRNA for mu- and delta-chains

Although IgD is expressed on the surface of resting B cells at a higher density than IgM, we determined that both the steady-state level and the biosynthetic rate of mu m-mRNA is higher than that of delta m-mRNA, suggesting that translational or post-translational processing of the Ig heavy chains may modulate the expression of cell surface Ig. After B cell activation by LPS, delta m-mRNA decreases drastically, accounting for the observed decrease in expression of IgD. Concomitantly, a dramatic increase in the level of mu s- and gamma s-mRNA corresponds to the observed increase in secretion of these Ig isotypes in LPS-stimulated cells.

Lymphokine-induced IgM secretion by clones of neoplastic B cells

The induction of antibody secretion by B cells requires T-cell-derived factors1-5. Such factors have been described1,2,6-12 but the precise relationship among these various factors is not clear, and it has been difficult to demonstrate that these factors act directly on the B cell and do not exert their effect via T cells or macrophages. In this report we describe the direct induction of IgM synthesis and secretion in cloned lines of long-term tissue culture adapted neoplastic B cells (BCL1) by T-cell supernatants from phorbol-12-myristate 13-acetate (PMA)-induced EL-4 cells or concanavalin A (Con A)-induced 7.1.1a cells5,9. We have termed this activity BCDFmu (B-cell differentiation factor for IgM). The supernatants containing BCDFmu induce activated and neoplastic B cells to secrete IgM5 and the factor responsible is distinct from BCGF13, interleukin-2 (IL-2)5, the classical T-cell replacing factor (TRF) described by Schimpl and Wecker5, and immune interferon (IFN gamma)5.

Structural studies of cell surface and secreted IgG in LPS-stimulated murine B cells

We have characterized the cell surface IgG of LPS-stimulated B lymphocytes by surface iodination and specific immunoprecipitation. IgG3 was found to be the predominant IgG subclass expressed on the B cell surface after 5 days of stimulation with LPS. In contrast, IgG2b, IgG3, and IgG1 subclasses are all secreted. Cell surface IgG exhibits detergent binding characteristics not shown by secreted IgG and the gamma chains of the three subclasses of surface IgG examined have the apparent mol. wt of 64 Kd, some 9,000 larger than the H chains of secreted IgG.

Effect of lipopolysaccharide stimulation on the transcription and translation of messenger RNA for cell surface immunoglobulin M

Analysis of mu-specific mRNA in the B cell tumor line, BCL1, shows that the cells contain predominantly mRNA for mu chain of membrane-bound immunoglobulin M (IgM) (2.7 kb, mu m mRNA). Stimulation of the cells to Ig secretion by lipopolysaccharide (LPS) results in a 6-12 fold increase in amount of mRNA for the mu chain of secreted IgM (2.4 kb mu s mRNA). The increase in mu s mRNA is accompanied by a 3-4-fold increase in mu m mRNA. The rate of mu chain synthesis of membrane IgM in LPS-stimulated cells is, however, reduced by at least twofold, suggesting that both transcriptional and translational regulatory events are involved in the induction of B lymphocytes to secretion.

Characterization of a monoclonal antibody reactive with a subset of human breast tumors

Fusion of spleen cells, from mice immunized against the human hormone-dependent breast cancer cell line ZR-75-1, with murine myeloma cells resulted in the establishment of a hybridoma cell line, HY59-H10 (H59). The purified monoclonal IgM produced by the hybridoma reacts with the most differentiated human breast tumor cell lines but not with cells derived from normal breast secretions or with numerous other malignant cell lines. Of 106 biopsy specimens examined, H59 bound to 54% of malignant breast specimens, to 83% of fibroadenomas, and to 82% of specimens containing fibrocystic disease.

A peptide difference between the mu-chains from cell-associated and secreted IgM of the BCL1 tumor

The murine B cell tumor, BCL1, bears monomeric IgM lambda on its surface. After stimulation in vitro with LPS, the cells secrete pentameric IgM lambda. Comparison of mu-chains from radiolabeled intracellular, surface, and secreted IgM indicates that mu-chains from the three sites have different apparent m.w. Since the observed differences are analogous to those reported for normal murine lymphoid cells, the BCL1 cells were used for determining the structural basis for the differences in m.w. of mu-chains from the above sites. Comparative peptide analysis was performed on mu-chains from cell associated and secreted IgM. Approximately 25 peptides were identified after digestion with chymotrypsin and trypsin and analysis of peptides by cation exchange chromatography. All peptides co-eluted with the exception of a single extra peptide derived from the Fc portion of the secreted IgM. The same peptide was observed in a similar analysis using mu-chains from IgM secreted by normal splenocytes.

A peptide difference between the mu-chains from cell-associated and secreted IgM of the BCL1 tumor

The murine B cell tumor, BCL1, bears monomeric IgM lambda on its surface. After stimulation in vitro with LPS, the cells secrete pentameric IgM lambda. Comparison of mu-chains from radiolabeled intracellular, surface, and secreted IgM indicates that mu-chains from the three sites have different apparent m.w. Since the observed differences are analogous to those reported for normal murine lymphoid cells, the BCL1 cells were used for determining the structural basis for the differences in m.w. of mu-chains from the above sites. Comparative peptide analysis was performed on mu-chains from cell associated and secreted IgM. Approximately 25 peptides were identified after digestion with chymotrypsin and trypsin and analysis of peptides by cation exchange chromatography. All peptides co-eluted with the exception of a single extra peptide derived from the Fc portion of the secreted IgM. The same peptide was observed in a similar analysis using mu-chains from IgM secreted by normal splenocytes.

The kinetics and mechanisms of the gas phase pyrolyses of exo-2-norbornyl chloride and cyclopentyl chloride

The gas phase pyrolyses of exo-2-norbornyl chloride and cyclopentyl chloride were studied in the temperature range 570–670 K. The results obtained show that these compounds behave as typical secondary halides insofar as the kinetics of their hydrogen chloride elimination reactions are concerned. Labelling experiments showed that in the formation of both norbornene and cyclopentene, a cis-1,2 elimination with a deuterium isotope effect of ∼3 was involved. Nortricyclene also was produced from exo-2-norbornyl chloride, via a trans 1,3 elimination; this process is analogous to a fragmentation of the ionized molecule. No gas phase Wagner–Meerwein rearrangement was involved in the formation of either norbornene or nortricyclene.

Characterization of the spontaneous murine B cell leukemia (BCL1). III. Evidence for monoclonality by using an anti-idiotype antibody

We have raised an anti-idiotypic antibody against the cell surface IgM of the murine BCL1 tumor cells. This antiserum reacts exclusively with the IgM expressed on the tumor cells and detects a unique population of cells in the spleen and blood of the tumor-bearing mice. When these cells are stimulated in vitro with LPS, they secrete an IgM bearing the same idiotype as the cell surface Ig. These results are discussed in terms of a model for the immunotherapy of a chronic lymphocytic leukemia-like syndrome in mice.

Characterization of the Spontaneous Murine B Cell Leukemia (BCL1)

We have raised an anti-idiotypic antibody against the cell surface IgM of the murine BCL1 tumor cells. This antiserum reacts exclusively with the IgM expressed on the tumor cells and detects a unique population of cells in the spleen and blood of the tumor-bearing mice. When these cells are stimulated in vitro with LPS, they secrete an IgM bearing the same idiotype as the cell surface Ig. These results are discussed in terms of a model for the immunotherapy of a chronic lymphocytic leukemia-like syndrome in mice.

A dichotomy between the expression of IgD on B cells and its requirement for triggering such cells with two T-independent antigens

The majority of adult B lymphocytes in the mouse bear two immunoglobulin isotypes, IgM and IgD (mu(+)delta(+) cells) (1). A small population of IgM-bearing cells lacks, or expresses very low levels of IgD (mu- predominant [mup] cells) (1). These cells are believed to constitute a less mature subset of B cells analogous to neonatal B cells (2). Based on the time during ontogeny when responses to T-independent (TI) and T-dependent (TD) antigens appear (3, 4) and the ability to block in vitro responses with anti- mu or anti-delta (5, 6, D. Mosier, personal communication), it has been suggested that the precursors of two TI-1 responses, trinitrophenyl (TNP)- Brucella (TNP-BA) and TNP-lipopolysaccharide (TNP-LPS) are mup cells (5, 6), whereas the precursor for a TD response, TNP-sheep erythrocytes (TNP-SRBC), bears both IgM and IgD (6). However, the possibility cannot be excluded that IgD is present on some or all of the TI precursors, but that it is not obligatory for triggering. In the present experiments we have examined the phenotypes of TI and TD precursors by treating cells with C' and either anti-mu or anti-delta before stimulation with antigen. Our results suggest that the majority of B cells that respond to TNP-BA, TNP-LPS, and TNP-SRBC bear IgD, even though in the case of the two TI antigens, IgD is not required for triggering.

Cell surface immunoglobulin XXI. appearance of IgD on murine lymphocytes during differentiation

The differentiation of Ig-bearing lymphocytes in adult mice was studied by monitoring the appearance of IgD relative to IgM on the surface of splenocytes obtained from lethally irradiated animals reconstituted for various periods of time with adult bone marrow cells, neonatal splenocytes, or Ig- adult splenocytes. It was found that IgM appears before IgD on differentiating lymphocytes. Furthermore, the rate of appearance of IgD during differentiation of adult cells is similar to that observed with neonatal cells.

Cell surface immunoglobulin. XX. Antibody responsiveness of subpopulations of B lymphocytes bearing different isotypes

Murine spleen cells were depleted of specific B-cell subpopulations bearing different immunoglobulin isotypes by means of complement-mediated cytolysis after treatment with antisera specific for micron- and gamma-chains. The functional effect of this depletion was measured by assaying both the primary and secondary plaque-forming cell responses of the residual cells after transfer to carrier-primed lethally irradiated hosts. The results suggest that cells bearing IgM are the progenitors of plaque-forming cells in the primary response and cells bearing IgG are the major progenitors of IgG plaque-forming cells in the secondary response. The quantity of IgM on progenitors of secondary IgM plaque-forming cells decreases markedly as the interval between primary immunization and antigenic challenge increases. Long-term memory cells for the secondary IgM response bear small amounts of both IgM and IgG.

Partial characterization of nervous system-specific cell surface antigen(s) NS-2

Partial biochemical characterization of several neural tissue specific antigens isolated from a murine glioblastoma cell line was accomplished by means of radioiodination of intact cells followed by immunoprecipitation of the cell lysate with a rabbit serum specific for neural tissue antigens. Polyacrylamide gel electrophoresis of the immunoprecipitate in sodium dodecyl sulfate resolved the labeled antigens into several major components: two proteins (or glycoproteins) having apparent m.w.'s of 84,000 and 120,000 and lipid associated components which may be heterogeneous. The protein and lipid associated components apparently possess independent antigenicity because after chloroformmethanol extraction the protein components can be immunoprecipitated from the aqueous phase and the lipid associated component can be immunoprecipitated from the organic phase. Despite their independent antigenicity it is not known whether the components may be noncovalently associated on the cell surface. Although some of these antigens can be isolated from brain or glioma cells (a related tumor), non can be demonstrated in lymphoid tissues or C1300 neuroblastoma cells using identical methods. Therefore, these studies confirm our previous findings concerning the specificity of the anti-NS-2 antiserum by using cytotoxicity tests.

Stability of ribosomal and transfer ribonucleic acid in Escherichia coli B/r after treatment with ethylenedinitrilotetraacetic acid and rifampicin

A short treatment with ethylenedinitrilotetraacetic acid to permeabilize bacteria for various antibiotics or treatment with the ribonucleic acid (RNA) synthesis inhibitor rifampin causes a slow degradation of 50S and 30S ribosomal particles and of the corresponding 23S and 16S ribosomal RNA species (about 25 percent in 1 h). The effects are additive such that the decay is about 50 percent/h if rifampin is employed after permeabilization by ethylenedinitrilotetraacetic acid. The 5S ribosomal RNA and transfer RNA are essentially stable under these conditions.