Biomedical subjects

F D Finkelman

Publications and source records attributed to F D Finkelman.

At least 145 records · Page 8Linked to original sources

PubMed1990

Murine B cells expressing Thy-1 after in vivo immunization selectively secrete IgE.

IL-4 induces Thy-1 expression and IgE secretion by LPS--and T cell-stimulated murine B cells in vitro. IFN-gamma inhibits both of these IL-4-mediated effects. IL-4 and IFN-gamma are often exclusively produced by different CD4+ T cell subsets. Injection of mice with a polyclonal goat anti-mouse IgD antibody (GaM delta) stimulates large increases in the serum concentration of IgE through the production of IL-4. Neutralization of endogenous IFN-gamma production in GaM delta-injected mice leads to further increases in serum IgE levels. We show that IL-4 and IFN-gamma, produced after GaM delta injection, respectively, stimulate and inhibit the number of splenic B cells expressing Thy-1 in vivo. Increased numbers of Thy-1-expressing B cells are observed concomitantly with the onset of enhanced IgE secretion. These Thy-1-expressing B cells are highly and selectively enriched for IgE-secreting cells.

Animals↗

PubMed1990

Genetic analysis of the presentation of minor lymphocyte-stimulating determinants. II. Differing non-MHC control of super-stimulatory and more poorly stimulatory Mls phenotypes.

Analysis of the capacity of splenocytes from non-prototypic Mlsa or Mlsc mouse strains to stimulate allogeneic H-2k-compatible T cells in a primary Mls-defined MLR provided interesting examples of exceptions to the usually stated characterization of Mlsa and Mlsc determinants as highly stimulatory of weakly stimulatory, respectively. Across the Mlsa barrier, MA/My stimulator cells had a significantly reduced capacity to elicit responder proliferation in comparison with prototypic AKR/J or less well studied C58/J, CE/J, or RF/J splenocytes. Across the Mlsc barrier, a gradient of stimulatory ability was observed with RF/J splenocytes being virtually nonstimulatory, prototypic C3H/HeJ splenocytes having an intermediate capacity, and CE/J and C58/J being highly stimulatory presenters of this non-MHC specificity. The differing capacity of each of these H-2k stimulator cells to elicit unprimed responder cell proliferation across an Mlsa or Mlsc difference correlated with the T cell growth factor activity that was secreted into the MLR supernatants. The super stimulatory form of Mlsc was expressed in an autosomal dominant fashion by (Mlsc poorly stimulatory x Mlsc super-stimulatory)F1 animals, (BALB.K x C58/J)F1 or (RF/J x CE/J)F1. The segregation of Mlsc stimulatory ability among first backcross and F2 animals derived from the former F1 was compatible with a single non-MHC gene controlling the expression and presentation of the super-stimulatory form of Mlsc. The regulatory nature of this gene was indicated by the observation that F1 animals generated from the Mlsc nonprototypic and poorly stimulatory BALB/c parental strain were self-tolerant to the super-stimulatory form of Mlsc. The existence of an Mls specificity other than a and c was suggested by positive non-MHC MLR responses in certain responder/stimulator cell combinations of Mls prototypic and nonprototypic mouse strains.

Animals↗

PubMed1990

Monovalent ligands of complement receptor 2 inhibit whereas polyvalent ligands enhance anti-Ig-induced human B cell intracytoplasmic free calcium concentration.

We have performed experiments to investigate the role of ligands for complement receptor 2 (CR2) in human B cell activation. Flow microfluorimetry was used to assess changes in free intracytoplasmic calcium concentration [Ca2+] in indo-loaded B cells, immediately after exposure to anti-mu antibody and to monovalent or polyvalent CR2 ligands. As monovalent ligands we used the C3d fragment and synthetic C3 peptides (peptides P14, residues 1201-1214, and P28, residues 1187-1214). As polyvalent ligands we used i) an intact monoclonal mouse anti-CR2 antibody (HB5) and its F(ab')2 fragment, ii) tetravalent P13 [residues 1202-1214) 4-template), and iii) P28 conjugated to BSA (molar ratio 5/1). Anti-CR2 antibody HB5, tetravalent P13, and P28 conjugated to BSA, enhanced the ability of F(ab')2 fragments of the IgG fraction of goat anti-human mu antibody to increase human B cell [Ca2+]i. In contrast, the monomeric CR2 ligands C3d and P28 inhibited the anti-mu-induced increase in human B cell [Ca2+]i. Multivalent P13, P28, and the HB5, by themselves, did not affect B cell [Ca2+]i. These experiments suggest that the valence of the CR2 ligands is crucial for the nature (synergistic vs antagonistic) of the message transmitted through the CR2.

Antigens, Differentiation, B-Lymphocyte↗

PubMed1990

Interactions between murine B lymphocyte surface membrane molecules. Loaded but not free receptors for complement and the Fc portion of IgG co-cap independently with cross-linked surface Ig.

We have investigated the possible physical interactions between CR, receptors for the Fc gamma R and surface Ig (sIg) on the surface membrane of murine B lymphocytes. We used the rat mAb to murine CR, 8C12, and 7G6, as CR ligands, and soluble Ag-antibody complexes as FcR ligands; and F(ab')2 fragments of rabbit antibodies specific for mouse IgM and IgD as sIg ligands. We have found that: 1) sIg, CR, and Fc gamma R are not directly linked, because capping of any one did not affect the expression of the others; 2) the mAb 8C12 and 7G6 failed by themselves to cross-link CR; 3) soluble Ag-antibody complexes crosslinked some, Fc gamma R on a minority of Fc gamma R+ lymphocytes; 4) once loaded with anti-CR mAb, CR co-capped with sIg when sIg was cross-linked; 5) once loaded with Ag-antibody complexes, Fc gamma R also co-capped with sIg when sIg was sIg was cross-linked; 6) loading of Fc gamma R did not affect the co-capping of surface CR with cross-linked sIg and conversely, loading of CR did not affect the co-capping of Fc gamma R with cross-linked sIg; only loaded CR or Fc gamma R co-capped with sIg regardless of the status of the other surface molecule; 7) neither loaded nor free CR co-capped with cross-linked Fc gamma R, and neither loaded nor free Fc gamma R co-capped with cross-linked CR. These results demonstrate that both Fc gamma R and CR independently become associated with sIg when either receptor is loaded and sIg is cross-linked.

Animals↗

PubMed1990

Cross-linking Fc receptors stimulate splenic non-B, non-T cells to secrete interleukin 4 and other lymphokines.

Spleen cell populations depleted of both B and T lymphocytes produce interleukin 4 (IL-4) in response to stimulation with immunoglobulins bound to the surface of culture dishes. In the presence of interleukin 3 (IL-3), plate-bound (PB) IgE and PB-IgG1, IgG2a, and IgG2b are excellent stimulants, whereas PB-IgA and PB-IgM fail to stimulate IL-4 production. In the absence of IL-3, PB-IgE stimulates relatively modest production of IL-4, whereas PB-IgG2a generally does not. The response to PB-IgE is inhibited by soluble IgE; antibody to Fc gamma receptor II inhibits the response to PB-IgG2a. Thus, separate receptors mediate these stimulations, and Fc receptor cross-linkage is required for IL-4 production. Depletion of cells expressing asialo-GM1 does not diminish IL-4 production in response to PB immunoglobulins, indicating that natural killer cells are not essential for non-B, non-T cell production of IL-4. In addition to IL-4, non-B, non-T cells produce IL-3, but no detectable interleukin 2 or interferon gamma. Non-B, non-T cells may be an important source of lymphokines in a variety of immune responses and may serve to amplify the effects of T cells of the TH2 type.

Animals↗

PubMed1990

Characterization of murine complement receptor type 2 and its immunological cross-reactivity with type 1 receptor.

We have previously demonstrated that some mAbs prepared against mouse complement receptor type 1 (CR1) bind a 150,000 Mr protein in addition to the 190,000 Mr CR1 protein. We now identify the 150,000 Mr murine protein as complement receptor type 2 (CR2), since: (i) one of the monoclonal antibodies that bind this protein inhibits rosette formation between mouse B cells and C3d-bearing sheep erythrocytes; (ii) as is known for human CR2, this protein is present on B lymphocytes but not T lymphocytes; and (iii) this protein must have affinity for C3b, since it has weak factor I cofactor activity. In addition, this protein resembles the 145,000 Mr human CR2 molecule in size. Since four of the five mAbs that were produced by immunization with CR1 also bound CR2, and they bind to different CR1 epitopes, it seems that murine CR1 and CR2 share multiple epitopes. Injection of mice with one of the CR1-CR2 cross-reactive mAbs almost eliminated both CR1 and CR2 expression, but did not decrease B cell numbers or the expression of B cell IgM, Ia, or B220 antigens. In contrast, injection of mice with a non-cross-reactive anti-CR1 antibody only modulated CR1 expression. These antibodies should thus provide useful tools for the study of the in vivo roles of B cell complement receptors.

Animals↗

PubMed1990

New mouse models for chronic Cryptosporidium infection in immunodeficient hosts.

Cryptosporidium sp. causes fulminant diarrhea and chronic infection in immunocompromised, particularly human immunodeficiency virus-infected, persons. The lack of in vitro cultivation and a suitable animal model has limited development of effective treatment. We describe two new mouse models of chronic symptomatic cryptosporidiosis in adult athymic mice and in T-cell subset-depleted mice. A progressive infection, fatal within 4 months, occurred in most adult athymic mice; a few developed stable infections. Symptoms included dehydration, weight loss, intermittent diarrhea, and jaundice. Pathologic abnormalities and organisms localized in the intestine in stable infections but involved the hepatobiliary tree and pancreas in others. Lymphoid cells from histocompatible, Cryptosporidium sp.-immune mice cured infected nude mice. Identical infections occurred in neonatally infected BALB/c mice treated with anti-CD4 monoclonal antibodies alone or also with anti-CD8 monoclonal antibodies; the mice were cured when the monoclonal antibody treatments were stopped. These models will be useful in definition of the immune defects that permit chronic cryptosporidiosis to develop and in assessment of treatment modalities.

Animals↗

PubMed1990

Lymphokine control of in vivo immunoglobulin isotype selection.

Several specific conclusions can be drawn from these studies: 1. IL-4 is required for the generation of both primary polyclonal and secondary antigen-specific IgE responses in vivo. 2. IL-4 is required to maintain established, ongoing, antigen-specific and polyclonal IgE responses. 3. Most, but not all, polyclonal IgE production during a secondary immune response is IL-4-dependent. Memory B cells that have already switched to IgE at the DNA level may no longer require stimulation with IL-4 to be induced to secrete IgE. 4. The generation of a secondary IgE response is not dependent upon the presence of IL-4 during primary immunization. However, if IL-4 is not present during primary immunization, it is required during secondary immunization for the generation of an IgE response. 5. IL-4 does not appear to be required for the generation of in vivo IgG1 responses, and in at least some instances, does not contribute significantly to the generation of IgG1 responses in vivo. 6. A late-acting form of T-cell help other than IL-4 appears to be required for the generation of an IgE, but not an IgG1 response. 7. An antibody that inhibits IL-4 binding to IL-4 receptors affects Ig isotype selection in the same way as an antibody that neutralizes IL-4. 8. IFN-gamma can act in both spontaneous and induced immune responses to suppress IgE production. 9. IFN-gamma can also suppress IgG1 production and stimulate IgG2a production. However, IFN-gamma appears to suppress polyclonal IgG1 responses more than antigen-specific IgG1 responses, and it enhances, but is not required for, the generation of IgG2a responses. 10. IFN-alpha appears to resemble IFN-gamma in its ability to inhibit IgE and enhance IgG2a responses in GaM delta-injected mice, but it requires the presence of IFN-gamma to suppress IgG1 production in these mice. 11. Both IFN-alpha and IFN-gamma appear to be able to decrease IgE production in some human patients. 12. There is no direct evidence that IL-5 contributes to the generation of in vivo antibody responses. Two general conclusions may also be drawn.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Differential regulation of murine B cell Fc gamma RII expression by CD4+ T helper subsets.

The murine B cell FcR for IgG (Fc gamma RII) is a membrane glycoprotein reported to mediate inhibition of B cell activation and differentiation. We show that IL-4 inhibits the enhanced expression of Fc gamma RII by LPS-stimulated B cells. This activity is completely reversed by anti-IL-4 mAb and is specific, in that multiple other lymphokines tested do not exert a similar effect. This effect of IL-4 is apparent by day 1 of culture, although maximal inhibition occurs on day 4 at a concentration of 500 U/ml. The IL-4-induced inhibition of enhanced Fc gamma RII expression by LPS stimulation observed on day 4 of culture is associated with a significant reduction in the steady state level of Fc gamma RII beta gene-specific mRNA. IFN-gamma which inhibits many of the effects of IL-4 on B cells, does not reverse the IL-4-induced inhibition of Fc gamma RII membrane expression nor the levels of beta gene-specific mRNA. Fc gamma RII expression is significantly increased in B cells stimulated with antigen-specific, CD4+ T cell clones of the Th1 type (i.e., IL-2 and IFN-gamma-producing). By contrast, three different Th2 clones (i.e., IL-4-producing) fail to stimulate an increase in Fc gamma RII levels. Anti-IL-4 mAb significantly enhanced Fc gamma RII expression by Th2-stimulated B cells indicating that IL-4 was the active, inhibitory, substance produced by the Th2 cells. Supernatants from stimulated Th2 clones inhibited the enhanced expression of Fc gamma RII by LPS-stimulated B cells and this activity was completely reversed by anti-IL-4 mAb. By contrast, supernatants from stimulated Th1 clones further enhanced Fc gamma RII expression by LPS-stimulated B cells. The differential regulation of B cell Fc gamma RII expression by Th subsets may play an important role in the regulation of humoral immunity by altering the sensitivity of B cells to IgG immune complex-mediated inhibition of B cell activation and differentiation in vivo.

Animals↗

PubMed1989

Different patterns of inositol polyphosphate production are seen in B lymphocytes after cross-linking of sIg by anti-Ig antibody or by a multivalent anti-Ig antibody dextran conjugate.

Anti-delta antibody conjugated to 2 x 10(6) m.w. dextran (dex) stimulates B lymphocyte proliferation at 10,000-fold lower concentrations than that required by the unconjugated antibody. Dex conjugated antibody also stimulates a greater and more sustained increase in intracellular ionized calcium [( Ca2+]i) than does the unconjugated anti-Ig antibody. Inasmuch as inositol phosphate metabolites have been linked to rises in [Ca2+]i, we analyzed by FPLC the relative amounts of the inositol polyphosphates (IP) in these cells. Anti-Ig-dextran induced a threefold greater increase in total IP than did the unconjugated anti-Ig. Furthermore, in cells stimulated by unconjugated anti-Ig there was a transient induction of I(1,4,5)P3 followed by a rapid accumulation of the I(1,3,4)P3 isomer with little accumulation of I(1,4)P2, whereas in anti-Ig-dex-stimulated cells there was prolonged elevation of I(1,4,5)P3 with more accumulation of I(1,4)P2. In addition, levels of I(1,3,4,5)P4 were maintained over a longer period of time in B cells stimulated by anti-Ig-dex than in those stimulated by unconjugated anti-Ig. The enhanced ratio of I(1,4,5)P3/I(1,3,4)P3 was also seen when suboptimal concentrations of anti-Ig-dex were used which stimulated a level of total inositol phosphate that was similar to that stimulated by the unconjugated anti-Ig. The possibility that the greater stimulation of increased [Ca2+] by anti-Ig-dex than by unconjugated anti-Ig was a predominant factor in influencing the metabolic pathway of I(1,4,5)P3 was excluded. These results show that 1) stimulation of increases in the various IP isomers occurs in anti-Ig stimulated normal B cells as has been shown in B cell lines and 2) that signal transduction and consequent PIP2 hydrolysis that is stimulated by Ag-mediated cross-linking of sIg is strongly influenced by the extent and type of cross-linking that is induced.

Animals↗

PubMed1989

Neonatal suppression with anti-Ia antibody. III. In vivo responses to the type 2 antigen TNP-Ficoll.

We studied the response to thymus-independent type 2 (type 2) Ag in mice suppressed from birth with anti-Ia antibody. Although these mice have significantly reduced numbers of surface IgM+ cells and reduced or absent levels of Ia-restricted Th cell activity, their IgM antibody response to the type 2 Ag TNP-Ficoll was unaffected whereas that to the prototypic thymus-dependent Ag SRBC was predictably eliminated. These data suggest that an in vivo antibody response can be made to type 2 Ag in the absence of Ia-dependent cellular interactions. The surface IgM+IgD-Ia- B cells that are found in the anti-Ia antibody-suppressed mouse may represent an expanded population of Ia-independent, type 2 Ag-sensitive B cells normally present as a smaller proportion of the splenic lymphocyte population. Thymus-dependent responses, which have been shown to have an absolute requirement for an Ia-dependent interaction, are absent in these animals.

Animals↗

PubMed1989

T help requirements for the generation of an in vivo IgE response: a late acting form of T cell help other than IL-4 is required for IgE but not for IgG1 production.

To further define requirements for T cell help in the stimulation of an in vivo IgE response, we studied a system in which the injection of mice with a goat antibody to mouse IgD (GaMD) stimulates large polyclonal IgG1 and IgE responses. In this system, both responses are blocked by anti-CD4 antibody, but only the IgE response is blocked by (anti-IL-4) antibody. Anti-CD4 antibody, if injected 5 days after GaMD, was found to inhibit the GaMD-induced IgE response to a much greater extent than the IgG1 response, even though both responses occur simultaneously and are inhibited to an equal extent by optimal or suboptimal doses of anti-CD4 antibody administered 2 days after GaMD. Even a suboptimal, 50-micrograms dose of anti-CD4 antibody, when injected 5 days after GaMD, inhibited the IgE response to a much greater extent than did an optimal 10-mg dose of anti-IL-4 antibody injected at the same time, even though 10 mg of anti-IL-4 antibody more completely inhibited GaMD-induced IgE production than did 50 micrograms of anti-CD4 antibody when injected 2 days after GaMD. These observations provide evidence that a late acting form of T cell help other than IL-4 is important for the generation of an IgE response but not an IgG1 response in GaMD-immunized mice.

Animals↗

PubMed1989

Control of in vivo IgE production in the mouse by interleukin 4.

In vitro studies have demonstrated that the cytokine IL-4 can, with the proper co-stimuli, induce IgE secretion. We have demonstrated in in vivo studies with a monoclonal anti-IL-4 antibody that this cytokine is required for the generation of the polyclonal primary IgE responses induced by injecting mice with GaM delta antibody or inoculating them with larvae of the nematode parasite Nippostrongylus brasiliensis (Nb), as well as for the secondary TNP-specific IgE response induced by immunizing mice with TNP-KLH on alum. We now report studies that demonstrate that: (1) the secondary polyclonal IgE response induced by repeated Nb inoculation, while mostly inhibitable by anti-IL-4 antibody, has an IL-4-independent component; (2) whereas treatment with anti-IL-4 antibody during a primary Nb inoculation does not prevent the rapid generation of a large IgE response during a second inoculation, treatment with anti-IL-4 antibody during both primary and secondary inoculation inhibits the development of a secondary IgE response by greater than 99%; (3) an established ongoing chronic IgE response, induced by inoculation of mice with larvae of the nematode parasite Heligmosomoides polygyrus (Hp), can be reduced by greater than 95% by administration of anti-IL-4 antibody; and (4) an anti-IL-4 receptor antibody effectively, efficiently and selectively blocks the GaM delta antibody-induced IgE response. These observations suggest that approaches aimed at blocking IL-4 effects may be useful for treating IgE-mediated diseases.

Animals↗

PubMed1989

IgE secretion by Epstein-Barr virus-infected purified human B lymphocytes is stimulated by interleukin 4 and suppressed by interferon gamma.

The cytokine interleukin 4 (IL-4) has been shown to induce lipopolysaccharide-activated murine B cells to differentiate into IgE-secreting cells and to stimulate IgE secretion by cultured human peripheral blood lymphoid cells. It is unclear, however, whether this effect of IL-4 on human peripheral blood lymphoid cells is a direct effect on the B cell because IL-4 can stimulate T cells and monocytes as well as B cells and does not induce purified human B cells to secrete immunoglobulin. To investigate this issue we studied the ability of IL-4 to induce IgE secretion by purified human B cells (93-96% CD20+, less than 1% CD3+) that were cultured with Epstein-Barr virus (EBV). Although B cells cultured with IL-4 alone did not secrete Ig and B cells cultured with EBV alone secreted IgM, IgG, and IgA but less than 150 pg of IgE per ml, the combination of EBV and IL-4 induced an IgE response that ranged from 11.4 to 40.3 ng/ml of culture supernatant after 26 days of culture. While IL-4 also enhanced IgM, IgG, and IgA secretion, as well as proliferation by EBV-infected B cells, these effects were less pronounced, occurred earlier during culture, and required a lower concentration of IL-4 than did the stimulation of IgE secretion. Furthermore, interferon gamma at 10 units per ml was found to inhibit IL-4/EBV-induced IgE secretion without inhibiting the other stimulatory effects of IL-4. We conclude that (i) IL-4 and interferon gamma can act directly on polyclonally activated human B cells to respectively stimulate and suppress IgE secretion and (ii) IL-4, in addition to its specific effect on IgE secretion, has a general stimulatory effect on the growth and differentiation of EBV-infected human B cells.

B-Lymphocytes↗

PubMed1989

Surface immunoglobulin-mediated B-cell activation in the absence of detectable elevations in intracellular ionized calcium: a model for T-cell-independent B-cell activation.

We recently showed that anti-immunoglobulin conjugated to high molecular weight dextran is 1000-fold more mitogenic for B cells than unconjugated anti-immunoglobulin. This system serves as a model for T-cell-independent type 2 antigens such as haptenated Ficoll, dextran, and bacterial polysaccharides, which can also stimulate B-cell proliferation and antibody production at low concentrations. We show here that conjugated anti-immunoglobulin, at concentrations that stimulate significant increases in expression of major histocompatibility complex class II molecules and incorporation of thymidine into DNA, does not induce detectable modulation of surface immunoglobulin. These results indicate that the facilitated T-cell-independent B-cell activation by polysaccharide antigens may result from inability to modulate surface immunoglobulin, possibly resulting in persistent and/or repetitive signaling. Early large increases in Ca2+ and breakdown of inositol phospholipids presently thought to be involved in transduction of the mitogenic signal are not detectable at low concentrations of conjugated anti-immunoglobulin, raising the possibility that these biochemical events may not in fact be central to this signaling pathway.

Animals↗

PubMed1989

Altered expression of the Salmonella typhimurium-specific B-cell repertoire in mice chronically treated with antibodies to immunoglobulin D.

Using a modification of the splenic focus assay, we analyzed the Salmonella typhimurium-specific B-cell repertoire in salmonella-susceptible BALB/c mice. Although these mice normally succumbed to salmonella infection before antibody was produced, they appeared to have splenic S. typhimurium-specific B-cell precursors that could be activated to differentiate and secrete antibody in a manner which was quantitatively and qualitatively identical to that of salmonella-resistant mouse strains. We also analyzed the primary S. typhimurium-specific B-cell repertoire in BALB/c mice that had been chronically treated with antibodies to immunoglobulin D (IgD) and therefore had no surface IgD-positive B cells. Although the frequency of S. typhimurium-specific precursors in these mice was similar to that of control mice, there was an apparent alteration in the isotype distribution pattern in anti-IgD-treated mice. Control mice generated a significantly greater proportion of IgG-secreting clones than did anti-IgD-treated mice. In addition, a greater proportion of S. typhimurium-specific clones from control mice secreted IgG2 than secreted IgG1, and those clones that secreted IgG2 but not IgM, IgG3, or IgG1 were greater than 20-fold more common in control than in anti-IgD-treated mice. Finally, we analyzed the immune response of control and anti-IgD-treated mice to a live avirulent vaccine, S. typhimurium SL3235. Although both groups were protected after challenge with a live virulent S. typhimurium strain, only the control mice made serum antibodies to this vaccine. Taken together, these results show that (i) salmonella-susceptible BALB/c mice have S. typhimurium-specific B cells, (ii) the S. typhimurium-specific B cells in anti-IgD-treated mice may have a restricted capacity to switch heavy-chain classes, (iii) the similarity observed in the frequency of the S. typhimurium-specific precursors for these two groups of BALB/c mice is not reflected in the serum, and (iv) the failure of anti-IgD-treated mice to generate a serum antibody response to SL3235 in the face of complete protection suggests that this model may be used to study cell-mediated immune mechanisms in the apparent absence of humoral immunity.

Animals↗

PubMed1988

IL-4 is required to generate and sustain in vivo IgE responses.

Antibodies of the IgE isotype play a predominant role in immediate hypersensitivity reactions. IL-4, a T cell-derived lymphokine that stimulates increased Ia expression by resting B cells and increased IgG1 secretion by LPS-activated B cells in vitro, has also been shown to regulate in vitro and in vivo polyclonal IgE responses. We report that large quantities of a purified anti-IL-4 mAb inhibit primary in vivo polyclonal IgE responses by 99% in mice infected with Nippostrongylus brasiliensis or injected with anti-IgD antibodies, and totally inhibit secondary Ag-specific IgE responses to TNP-keyhole limpet hemocyanin without effect on either IgG1 or IgG2a responses to these stimuli. The lack of effect of anti-IL-4 antibody on IgG1 secretion cannot be explained simply by inadequate neutralization of IL-4, inasmuch as the doses of anti-IL-4 antibody used blocked an N. brasiliensis-induced increase in B cell Ia expression by more than 85%, whereas in vitro studies indicate that enhancement of B cell Ia expression requires less IL-4 than induction of IgG1 secretion. In addition to demonstrating that IL-4 plays a necessary role in the generation of an in vivo IgE response, we show that IL-4 has an important role in sustaining established IgE responses, because anti-IL-4 antibody, when given at the peak of an N. brasiliensis- or TNP-keyhole limpet hemocyanin-induced IgE response, accelerates the declines in total serum IgE and in IgE anti-TNP antibody levels, respectively. These observations suggest that the effects of IL-4 on in vivo immune responses may be more specific than might have been predicted from in vitro observations, and that regulation of IL-4 production or action may be useful for the prevention or therapy of immediate hypersensitivity disorders.

Animals↗

PubMed1988

Activation of CD 4-, CD 8- thymocytes with IL 4 vs IL 1 + IL 2.

Thymocytes from C57BL/6 mice were highly purified to obtain the CD 4-, CD 8- subpopulation which constitutes only 5% of all thymocytes. Substantial proliferation was induced in vitro with either IL-1 + IL-2 or with IL-4 in the presence of PMA. IL-1 and IL-2 synergized in inducing proliferation of these purified CD 4-, CD 8- thymocytes whereas neither synergized with IL-4. In order to determine whether stimulation with IL-1 + IL-2 acted via IL-4 or vice versa, cultures were treated reciprocally with affinity-purified anti-IL-2 or anti-IL-4 antibodies. Cultures with IL-4 were inhibited by anti-IL-4 but were unaffected by anti-IL-2. The CD 4-, CD 8- thymocytes cultured with IL-1 + IL-2 + anti-IL-2 were inhibited to baseline IL-1 stimulation. At low concentrations of IL-1 (1 U/ml) and IL-2 (100 U/ml), anti-IL-4 had no effect, whereas at higher levels of IL-1 (2 U/ml IL-1), and 100 or 200 U/ml IL-2, anti-IL-4 significantly reduced DNA synthesis. This result suggests that at higher concentrations the combination of IL-1 + IL-2 can induce cells to produce IL-4 which then contributes to overall proliferation. When CD 4-, CD 8- thymocytes were cultured with the low doses of IL-1 + IL-2 for 72 h, 62% expressed cell surface T3 complex (vs 11% at initiation) and 27% were F23.1+ (vs 5% at initiation). In contrast, culture with IL-4 led to no increase in numbers of T3+ cells and none were F23.1+; however, there was coexpression of Thy1 and 6B2 on 20% of cells at the end of culture (vs 4% at initiation). Thus, IL-1 + IL-2 causes expansion of a CD 4-, CD 8- thymocyte population expressing the alpha, beta-T cell receptor, whereas IL-4 induces cells to express a phenotype present in small numbers in the periphery of normal mice and in larger numbers in mice bearing the lpr gene.

Animals↗