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E Severinson

Publications and source records attributed to E Severinson.

At least 19 recordsLinked to original sources
PubMed1991

T and B cell collaboration: induction of motility in small, resting B cells by interleukin 4.

In this report we investigate if IL 4 can work as a chemoattractant factor by inducing locomotion in B cells. We found that murine recombinant IL 4 (rIL 4) induced motile morphology and migration through polycarbonate micropore filters of murine, splenic B cells at an optimal concentration of 3 ng/ml. Kinetic studies revealed optimal migration at 8-16 h, although a significant response could be detected already after 1 h. Flow cytometric studies confirmed that the migrated cells were indeed B cells. We also compared the activity of small, dense B cells and large, low-density B cells, based on Percoll gradient separation. We found no difference in IL 4-induced motility among the two groups. Furthermore, we looked at B cells activated in vitro by preculture in lipopolysaccharide (LPS) or IL 4. Our data indicate that both LPS and IL 4 can increase the general capacity for motility in B cells after preculture for 24 h. T and B cell collaboration requires close cell-cell contacts in order for T cell help to be administered to the B cell. One way of enhancing such cell contacts could be through directional cell migration induced by helper factors (chemotaxis). We suggest that IL 4 can play a role as a chemoattractant factor that enhances cell contacts between T helper cells and B cells.

Animals↗
PubMed1990

Cholera toxin acts synergistically with IL-4 to promote IgG1 switch differentiation.

Previously, we reported that cholera toxin (CT) causes LPS-stimulated membrane (m)IgM+ B cells to undergo increased switch differentiation to IgG- and IgA-producing B cells. In this study we determined whether this effect is specific for one or several of the IgG subclasses and whether B cells exposed to CT respond differently to IL-4, a lymphokine with switching capabilities. In initial studies we found that in LPS-stimulated, mIgM+ B cell cultures, CT eightfold enhanced the formation of IgG1-producing B cells, whereas it only weakly enhanced, one- to twofold, the formation of IgG3-producing B cells. In addition, CT synergistically enhanced the induction of IgG1-producing B cells by IL-4, even at plateau concentrations of IL-4. In contrast, IgM and IgG3 responses were suppressed in the CT plus IL-4-containing cultures as compared to those containing only LPS or LPS and CT. Furthermore, CT plus IL-4 had no enhancing effect on the formation of cells producing IgA; on the contrary, the presence of IL-4 led to a reversal of the stimulatory effect of CT on the IgA response. In further studies, we found that CT affected B cell differentiation at the gene level, before final gene recombination has occurred. Thus, CT together with LPS induced faint but detectable germline gamma 1 RNA transcripts not seen with cells cultured in LPS alone. However, more strikingly, CT enhanced by several-fold expression of germline gamma 1 RNA transcripts in LPS-stimulated B cell cultures containing optimal IgG1-inducing concentrations of IL-4. In addition, despite its weakly positive effect on IgG3 production. CT inhibited expression of germline gamma 3 RNA transcripts in cultures containing LPS and caused a further decrease in such transcripts in cultures containing LPS and IL-4. Finally, we found that CT enhanced the in vivo IgG1 but not the IgG3 or IgM anti-DNP serum antibody response of mice immunized with DNP-LPS. Taken together, these studies suggest that CT more strongly promotes B cell differentiation to IgG1 than to any other IgG subclass in LPS-stimulated cultures. CT acts alone or in synergy with IL-4, early in B cell differentiation to promote IgG1 expression in LPS-stimulated B cell cultures, probably by inducing early steps in the switch to this isotype such as the production of germline gamma 1 RNA transcripts.

Animals↗
PubMed1990

Induction of germ-line immunoglobulin heavy chain transcripts by mitogens and interleukins prior to switch recombination.

It has recently been postulated that immunoglobulin class switching is preceded by transcription from unrearranged heavy chain genes. In this report, we have investigated the conditions under which RNA transcribed from unrearranged C gamma 3, C gamma 1, C gamma 2b, C gamma 2a, C epsilon and C alpha genes are induced in normal spleen cells by mitogens and/or interleukin (IL) 4, IL 5 and interferon-gamma. Lipopolysaccharide (LPS) plus IL 4 induced germ-line gamma 1 and epsilon transcripts. LPS induced gamma 2b and gamma 3 transcripts and high doses of IL 4 suppressed these LPS-induced transcripts. Interferon-gamma induced low levels of germ-line gamma 2a transcripts and profoundly suppressed the gamma 1 and epsilon transcripts induced by LPS and IL 4. IL 5 alone or in combination with IL 4 and/or LPS did not induce germ-line alpha transcripts. Spleen cells of the partially immunodeficient mice CBA/N and C3H/HeJ, which do not express IgG3 could be induced, however, by polyclonal activators to express germ-line gamma 3 and gamma 2b transcripts. The data indicate that the capacity of a ligand to induce/suppress transcription of a particular unrearranged heavy chain gene is a good indicator of its capacity to induce switching to the corresponding Ig isotype. However, it is also clear that control of switching can be carried out at other levels.

Animals↗
PubMed1990

Frequencies of interleukin-5 mRNA-producing cells in healthy individuals and in immunoglobulin-deficient patients, measured by in situ hybridization.

Interleukin-5 (IL-5) has previously been demonstrated to enhance immunoglobulin synthesis, especially IgA. Thus, it could be hypothesized that a defect production of IL-5 may cause immunoglobulin deficiency. We have analysed the frequency of IL-5 mRNA-producing cells in healthy adults and in patients with common variable immunodeficiency or selective IgA deficiency. Unstimulated lymphocytes were rarely found to synthesize IL-5 as measured by in situ hybridization. However, pokeweed mitogen and several other activating ligands induced the synthesis of IL-5 mRNA in peripheral blood and spleen lymphocyte cultures. After pokeweed mitogen activation, the number of IL-5 mRNA-producing cells most often peaked on day 3 with a maximal frequency of around 1-2% of mononuclear cells. In a kinetic study we were unable to detect any peak frequency differences between healthy controls (mean 0.44%) and 20 patients (mean 0.58%). Thus, although IL-5 has been reported to be an important regulator of IgA synthesis, a defect production does not seem to be the underlying mechanism in human immunoglobulin deficiency.

Adult↗
PubMed1989

Interleukin 4 induces synthesis of IgE and IgG4 in human B cells.

Interleukin (IL)4 has been shown to regulate the IgG subclasses and induce IgE production in splenic mouse B cells. Here we show that IL4 and phorbol 12-myristate 13-acetate (PMA) induce, on a per cell basis, very high IgE secretion in purified human B cells by using a mouse thymoma (EL4) co-culture method. In addition, a marked increase in the number of IgG4-producing cells was also observed. Furthermore, IL2 could synergize with IL4 and PMA in the production of IgE. By using limiting dilution analysis, a considerable increase in the precursor frequency for IgE was found when IL4 and PMA were added to cultures as compared to cultures with PMA only. This indicates that IL4 induces an isotype switch in human B cells.

Antibody Formation↗
PubMed1989

Regulation of IgG1 and IgE synthesis by interleukin 4 in mouse B cells.

Mouse interleukin 4 (IL-4) has been shown to act on B cells as an induction factor for Ig class switch. We studied the characteristics of IL-4-regulated Ig isotype production in lipopolysaccharide (LPS)-stimulated splenic B-cell cultures with emphasis on the comparison between the IgG1 and IgE responses. The results show that the kinetics for the appearance of IgG1 and IgE isotypes are similar, but that the dose of IL-4 required for the induction of an IgE response is 3-10 times higher than that for an IgG1 response. No requirement for T cells was found for the induction of either isotype. Pre-incubation of cells for 24 h with IL-4 alone was sufficient to induce an IgG1 response when cells were recultured with LPS from days 1 to 6. However, the simultaneous presence of both IL-4 and LPS for at least 24 h was required for a detectable IgE response. For an optimal IgE response, IL-4 needed to be present for more than 72 h in LPS-activated cultures. The possible reasons for the different regulation of IgG1 and IgE responses are discussed.

Animals↗
PubMed1989

Establishment of a memory in vitro murine IgE response to benzylpenicillin and its resistance to suppression by anti-IL-4 antibody.

Regulation of a memory IgE antibody response may be different from the induction of a primary response and may, therefore, be more relevant to the study of allergic diseases and the therapeutic manipulation of IgE antibody formation. In this paper a murine hapten-specific in vitro memory IgE antibody response to benzylpenicilloyl(BPO)-KLH is described. The response was analyzed by determining the number of antibody-producing cells (APC) in an ELISA spot assay. Of the total number of BPO-specific APC (10,000 APC/10(6) cultured spleen cells), about 1% were IgE-producing cells (100/10(6) cultured cells), as detected on day 6 of culture. The level of the antibody response is antigen dose-dependent, and the detected APC are BPO specific. The memory IgE response is not inhibited by the addition of anti-IL-4 antibody (11B11), even at a high excess. In the presence of the mitogen lipopolysaccharide, it has been shown that switch of B cells to IgE is induced by IL-4, a process which can be inhibited by anti-IL-4 antibody. Because the antigen-induced IgE response cannot be inhibited by anti-IL-4 antibody, in vitro responding cells derived from BPO-KLH-preimmunized mice may, therefore, have already switched in vivo to IgE. On the other hand, B cells switching to IgE in a situation of cognate T-B cell interaction might receive IL-4 in a transsynaptical way from T cells which might not be accessible to inhibition by anti-IL-4 antibody. The identification of the two possibilities in situations of established allergic disorders will be decisive for determining whether pharmacological inhibition of IL-4 (or IL-4-induced switch)--e.g., by putative low molecular weight compounds--will ever be a meaningful approach to suppress allergic diseases.

Animals↗
PubMed1989

Interleukin 4 induces cellular adhesion among B lymphocytes.

We here report that interleukin 4 (IL-4) alone is able to induce cellular adhesion among mouse lymphocytes, and together with lipopolysaccharide (LPS), it increases the adhesion induced by LPS. The adhesion was inhibited by antibodies against IL-4. IL-4 appears to be acting mainly on B lymphocytes, since the response caused by IL-4 alone was much less sensitive to depletion of adherent cells than the LPS response. Depletion of T cells had no effect on IL-4- or LPS-induced adhesion. IL-4 could together with Con A, but not alone, induce adhesion among T cells. Cell clusters, which were formed after 2-3 days of LPS plus IL-4 stimulation, could be completely dissociated, and when the cells were recultured in medium, they readily started to reaggregate. The adhesion molecule lymphocyte function-associated antigen 1 (LFA-1) is, at least in part, involved in LPS plus IL-4-induced adhesion. Antibodies against LFA-1 inhibited the adhesion, but antibodies against other cell surface molecules were without inhibitory effect. Adhesion induced by IL-4 alone may involve other adhesion molecules than LFA-1.

Animals↗
PubMed1988

Interleukin 4 instructs uncommitted B lymphocytes to switch to IgG1 and IgE.

Mouse interleukin 4 (IL 4) is a T cell-produced lymphokine with multiple effects on different cells types of the hematopoietic lineages. IL 4 has pronounced effects on B lymphocytes, where it induces high levels of IgG1 and IgE secretion in lipopolysaccharide-stimulated cultures that would otherwise secrete predominantly IgG3 and IgG2b (of the non-IgM isotypes). An important question is how IL 4 exerts its effect. Two main possibilities exist: (a) IL 4 instructs uncommitted B lymphocytes to IgG1 and IgE production; (b) IL 4 selects and expands an already precommitted B cell. In this study we show, by the use of limiting dilution analysis, that IL 4 dramatically increases the precursor frequency of IgG1 and IgE-secreting cells with no significant effect on the clone size, clearly suggesting that IL 4 instructs uncommitted B cells to switch to IgG1 and IgE. The fraction of total Ig precursors that can switch to the two isotypes is furthermore high. The high precursor frequency for IgE obtained in the presence of IL 4 further demonstrates that IL 4 is an important modulator of IgE responses.

Animals↗
PubMed1988

Immunoglobulin heavy-chain switching may be directed by prior induction of transcripts from constant-region genes.

Immunoglobulin heavy-chain switching is effected by a DNA recombination event that replaces the C mu gene with one of the other heavy-chain constant-region (CH) genes located 3' to the C mu gene. How the specificity of this event is controlled is unknown. However, it has been shown that IgM+ cells capable of switching to specific isotypes have the corresponding unrearranged CH genes in an accessible or active chromatin state, as demonstrated by the fact that these specific CH genes are hypomethylated and are transcriptionally active. We now report that the RNAs transcribed from specific unrearranged CH genes are induced prior to switching under conditions that promote switching to these specific CH genes. For example, we find that bacterial lipopolysaccharide, which induces the IgM+ cell line I.29 mu to switch to IgA, induces transcripts from the germ-line C alpha gene(s) in I.29 mu cells prior to switch recombination. Two preparations of T-cell lymphokines (recombinant interleukin 4 and supernatant from the T-cell line 2.19, which contains interleukins 4 and 5) that promote switching to specific isotypes by lipopolysaccharide-treated spleen cells induce transcripts from the corresponding germ-line CH genes prior to expression of the new isotypes. For example, interleukin 4, which appears to be necessary for switching to IgE in vitro and in vivo, induces within 2 days large increases in germ-line C epsilon transcripts in lipopolysaccharide-treated spleen cells and in I.29 mu cells. The most straightforward interpretation of our data is that these lymphokines direct switching to specific isotypes by activating specific CH genes, making them accessible to the putative switch recombinase.

B-Lymphocytes↗
PubMed1987

Interleukin 4 (IgG1 induction factor): a multifunctional lymphokine acting also on T cells.

A cDNA encoding the murine interleukin 4 (IL4) (IgG1 induction factor/B cell-stimulating factor no. 1) was recently cloned (Noma et al., Nature 1986.319: 640; Lee et al., Proc. Natl. Acad. Sci. USA 1986. 83: 2061). In this report we tested recombinant IL 4 in various T cell assays. It was found that IL 4 activated the murine T cell line CTLL to increased DNA synthesis but not to growth. It also activated normal concanavalin A (Con A)-stimulated T cells both to increased DNA synthesis and to growth. These T cell growth factor-like activities were not inhibitable by anti-IL 2 receptor antibodies. Evidence is given that both Lyt-2+ and L3T4+ T cells responded to IL 4. Finally, IL 4 acted synergistically with phytohemagglutinin or Con A on normal T lymphocytes as well as on thymocytes. These data, as well as those of others, imply that lymphokines have a broader range of activity than previously anticipated.

Animals↗
PubMed1987

IgG1 induction factor: a single molecular entity with multiple biological functions.

A cDNA clone coding for the murine IgG1 induction factor has been isolated. The translation products directed by this clone were analyzed in different biological assays. The data obtained show that the IgG1 induction factor: Is involved in the regulation of IgG responses, by increasing IgG1 and decreasing IgG3 and IgG2b secretion; Induces hyper-Ia expression on resting B lymphocytes; Synergizes with anti-Ig in inducing DNA synthesis in resting B lymphocytes; Synergizes with DxS in inducing DNA synthesis by B lymphocytes; It induces DNA synthesis by either the T cell line CTL-L or Con-A blasts. Thus, this lymphokine in addition to IgG1 inducing activity has also BSF-1, BCGF-II and TCGF like activities. The fact that a single molecule can perform all the above listed functions has implications for our view of lymphocyte activation. It indicates that considering the B cell response as an ordered series of independently controlled events, is an oversimplified view of the dynamic process through which B cells are activated and also indicate the functional interconnection of the different elements of the immune system.

Amino Acid Sequence↗
PubMed1987

Production of a monoclonal antibody useful in the molecular characterization of murine T-cell-replacing factor/B-cell growth factor II.

T-cell-replacing factor (TRF) is a T-cell-derived factor required for terminal differentiation of activated B cells to immunoglobulin-secreting cells. Previous studies have shown that a murine T-cell hybrid (B151K12) produces factor(s) that (i) induce immunoglobulin secretion by the B-cell leukemia line BCL1 and secondary anti-2,4-dinitrophenyl IgG synthesis in vitro by dinitrophenyl-primed B cells (TRF activity) and (ii) cause proliferation of the BCL1 cells [B-cell growth factor II (BCGF-II) activity]. Both activities appear to be associated with the same molecule. Here we report the production of a monoclonal antibody to murine TRF. The monoclonal antibody, designated TB13, strongly inhibited both TRF and BCGF-II activities and absorbed TRF- as well as BCGF-II-active molecules produced by B151K12 and by Xenopus oocytes that had been injected with mRNA transcribed from plasmid pSP6K-mTRF23. Inhibition was linearly dependent on the concentration of both TB13 and TRF. Monoclonal antibody TB13 did not inhibit the activities of B-cell stimulatory factor 1, interleukin 1, interleukin 2, or interleukin 3. TRF activity in dissolved samples of immunoprecipitates obtained with TB13 was recovered after NaDodSO4/PAGE, in the fractions corresponding to a protein band at Mr 46,000. Our results indicate that monoclonal antibody TB13 recognizes a molecule that has both TRF and BCGF-II activities.

Animals↗
PubMed1987

IgG1 induction factor.

The IgG1 induction factor elevates the IgG1 response and reduces the IgG2b and IgG3 response in LPS-stimulated spleen cells. The factor is a lymphokine produced by T cells. The precursor frequency for cells secreting the IgG1 induction factor is at least tenfold lower as compared to those secreting interleukin 2. Some biochemical properties of the lymphokine are listed. The effects of gamma interferon in B cell-stimulated cultures are shown. Isolation of a cDNA clone coding for the IgG1 induction factor has been achieved and results of these studies are reviewed. Evidence is given that this lymphokine is the same as B cell stimulating factor 1, and we propose that it be renamed interleukin 4. Finally, the possible mechanisms of interleukin 4 are discussed.

Animals↗