B cell differentiation and interleukin 2 (IL2): corticosteroids interact with monocytes to enhance the effect of IL2

Analysis of glucocorticoid receptors and their apoptotic response to dexamethasone in male murine B cells during development

Glucocorticoids have an important role in the resolution of inflammation and clinically they are routinely used to treat allergies, asthma, sepsis, and autoimmune diseases. In addition, glucocorticoids are well recognized to negatively impact the development and function of T cells in the immune system by inducing apoptosis. Less is known however about glucocorticoid function in B lymphocytes. Herein, we demonstrate that the glucocorticoid receptor (GR) is present in B-cell populations isolated from both the spleen and the bone marrow. B-cell populations were found to express more GR than non-B-cell populations from both the spleen and the bone marrow. GR protein was found in all B-cell (B220+) developmental subsets (Mature IgM+IgD+, Immature IgM+IgD-, and Pro/Pre IgM-IgD-) isolated from spleen. GR staining intensity was varied among the B-cell developmental subsets and was found to be higher in B cells isolated from the spleen (secondary lymphoid organ) versus the bone marrow (primary lymphoid organ). Ex vivo cell culture of murine splenocytes and bone marrow lymphocytes indicated that dexamethasone stimulated apoptosis in all B-cell developmental subsets demonstrating glucocorticoid responsiveness. Furthermore, in vivo administration of dexamethasone to adrenalectomized mice reduced B-cell numbers in both spleen and bone marrow. These data suggest that glucocorticoid signaling has an important understudied role in B-cell life-or-death decisions.

Dexamethasone suppresses T cell-mediated immunity and enhances disease susceptibility to Eimeria mivati infection

The effect of dexamethasone (DEX) on Eimeria mivati infection in chickens was examined. Chickens given an extended DEX treatment produced significantly higher numbers of total oocysts following primary and secondary infections with E. mivati. Chickens treated with DEX intramuscularly or orally showed lower body weight gain in E. mivati infected or uninfected chickens as compared with the untreated group. Chickens given DEX intramuscularly showed a lower number of splenic lymphocytes. Flow cytometric analysis of lymphocyte composition revealed that the percentages of splenic lymphocytes bearing CD8 (cytotoxic-suppressor T cells), gamma delta T cell receptor (TCR 1), class II major histocompatibility or surface IgM antigens in DEX-treated chickens were lower than in controls, whereas the percentages of T lymphocytes expressing CD3, CD4 (helper T cells) or alpha beta TCR antigens were significantly higher. Furthermore, concanavalin A-induced lymphoproliferation, interleukin-2 (IL-2) and gamma-interferon (gamma-IFN) production by spleen lymphocytes were generally depressed in DEX-treated chickens. IL-2 production of E. mivati-infected chickens given oral DEX was significantly lower compared with the uninfected-DEX-treated group. Uninfected chickens treated with DEX intramuscularly showed a significantly lower gamma-IFN production compared with other uninfected groups. In contrast, serum IgG levels were enhanced in DEX-treated, E. mivati-infected chickens compared with untreated, infected chickens. These results suggest that enhanced disease susceptibility to coccidiosis in DEX-treated chickens may reflect a drug-mediated immunosuppression of cell-mediated immunity.

Effects of cytokines on the pituitary-adrenal axis in cancer patients

Cytokines, which include interferons (IFNs), interleukins (ILs), and tumor necrosis factor (TNF), are immunoregulatory proteins produced by lymphocytes and inflammatory cells. Several cytokines, most noteworthy IFNs and ILs, stimulate glucocorticoid secretion. In this study, the effects of variable doses and repetitive administration of IFNs and TNF on secretion of pituitary hormones and cortisol were measured. Patients were given for a period of 15 days on alternating days injections of IFN-beta (IFN-beta ser), 90 or 450 x 10(6) IU, IFN-gamma, 0.1-100 x 10(6) IU, or TNF 125-275 micrograms/m2. Sixty to 120 min after IFN-beta ser injection median levels of cortisol, adrenocorticotropin (ACTH), prolactin (PRL), and growth hormone (GH) rose two-fold. Urinary free cortisol excretion increased significantly during the day following IFN-beta ser administration. IFN-gamma > or = 30 x 10(6) IU caused a comparable rise in plasma cortisol. TNF induced two- to four-fold increases in ACTH and cortisol. The fact that increased cortisol secretion was associated with a rise in the level of ACTH as well as PRL and GH suggests that the cytokines increased cortisol by stimulating the anterior pituitary. The hormonal response induced by cytokines was unrelated to their pyrogenic effect, undiminished with repetitive treatment, and not dose-dependent above a threshold level. These observations reinforce the concept of a physiologic link between the immune system and the hypothalamic-pituitary-adrenal (HPA) axis.

Cystic fibrosis patients' B-lymphocyte response is resistant to the in vitro enhancing effect of corticosteroids

Cystic fibrosis is associated with an cAMP-regulated channel defect, which has been evidenced in many cell types including B lymphocytes. To document a B-cell dysfunction potentially related to this defect, we studied the in vitro IgG production by lymphocytes from 11 cystic fibrosis patients. B lymphocytes were co-cultured with autologous monocytes and stimulated with Staphylococcus aureus Cowan or with Nocardia-delipidated cell mitogen in the presence of low concentrations of IL2. Cystic fibrosis patients' cells produced amounts of IgG comparable with that of normal and control patients' cells. However, dexamethasone (10(-7) mol l-1) had no effect on the response of cystic fibrosis patients' cells, whereas it enhanced that of the latter two groups. This resistance of cystic fibrosis cells was true with concentrations of dexamethasone up to 10(-6) mol l-1, whereas this agent induced a dose-related enhancement from 10(-8) to 10(-6) mol l-1 in cultures of normal cells. Co-culture experiments showed that cystic fibrosis B lymphocytes themselves are resistant to the effect of dexamethasone. In contrast dexamethasone normally suppressed the anti-CD3 antibody-induced response of cystic fibrosis T cells in the presence of IL2 and the IL1 alpha- or beta-induced collagenase production of cystic fibrosis fibroblast cell lines. Thus cystic fibrosis B lymphocytes exhibit a selective defect which may interfere with the normal interactions between the hormonal and immune systems and may participate in the sensitivity of cystic fibrosis patients to bacterial bronchopulmonary infections.

IgE synthesis by chronic lymphocytic leukemia cells

The present results indicate that B cells isolated from chronic lymphocytic leukemia (B-CLL) from 11 of 14 patients are capable of specifically producing IgE upon costimulation with IL-4 and hydrocortisone (HC). IgE is detected by intracytoplasmic fluorescence staining and by RIA. Clinical, hematological, and immunological parameters (including Rai stage, WBC, Lc, sIg kappa/lambda, CD5, and CD23 expression) cannot distinguish the IgE responder from the nonresponder patients. IL-4 alone is a potent inducer of human IgE synthesis by normal PBMC and we show here that its effect is strikingly enhanced by HC. The IgE produced by B-CLLs are monoclonal since they display the same L chain type as the freshly isolated CD5+ B-CLLs. We, therefore, conclude that the combination of IL-4 and HC can abrogate the maturation arrest of CD5+ B-CLLs by inducing their differentiation into IgE-producing cells. The present data provide a unique model to study the isotype switching to IgE and the regulation of human IgE synthesis by monoclonal human B cells.

Interleukin (IL) 4 counteracts the helper effect of IL2 on antigen-activated human B cells

We tested the effect of interleukin (IL) 4 on the specific IgM antibody response induced by trinitrophenylated-polyacrylamide beads (TNP-PAA) in cultures of human B cells. T cell help was provided by exogeneous IL2. IL4 profoundly suppressed the response to optimal concentrations (50 U/ml) of IL2, with a 50% inhibitory concentration of 6 U/ml. This was due neither to a shift in the kinetics nor to a switch to an IgG response. The production of anti-TNP antibody (as measured by an enzyme-linked immunosorbent assay in the culture supernatant) was inhibited to the same extent as the generation of plaque-forming cells. The effect of IL4 was completely abolished by a neutralizing antibody toward IL4. Kinetic studies showed that IL4 had to be present during the first 48 h of culture to fully inhibit the response. The sequential stimulation of B cells by antigen and by IL2 showed that IL4 does not negatively interfere with signaling through membrane Ig but counteracts the effect of IL2 on antigen-activated B cells.

Glucocorticosteroid-dependent synergy between interleukin 1 and interleukin 6 for human B lymphocyte differentiation

In order to analyze the effects of interleukin (IL) 6 on human in vitro Ig production B lymphocytes were activated by Staphylococcus aureus Cowan strain I (SAC) in the presence of low concentrations of IL2 (1 U/ml) and dexamethasone (10(-7) M). Previously we showed that this model of B cell response is completely monocyte dependent. We here demonstrate that, under these experimental conditions, IL6 is able to replace monocytes and stimulate Ig production provided IL1 is also present. Dose-effect curves show that these two monokines act synergistically. This synergy is demonstrable only in the presence of dexamethasone, when B lymphocytes are activated (by SAC) and when T cell help (provided by IL2) is present. It results in the production of both IgM and IgG. Both IL1 and IL6 have to be present during the first 48 h of culture to exert an optimal effect. These results show that IL6 may act on early (as well as on late) stages of normal B lymphocyte differentiation. Moreover, glucocorticosteroids potentiate the synergistic effect of IL1 and IL6 on their B lymphocyte target, an effect comparable to that exerted on hepatocytes.

Induction of differentiation in human leukemic B cells by interleukin 2 alone: differential effect on the expression of mu and J chain genes

The effects of interleukin 2 (IL2) on the proliferation and differentiation of B cells were analyzed separately using cells from two patients suffering from B-type chronic lymphocytic leukemia. The monoclonal B cells from these patients exhibited an opposite pattern of responsiveness upon in vitro culture with IL2 in the absence of other stimuli. In the first patient, IL2 alone was able to induce DNA synthesis and no Ig production. In the second patient, although no DNA synthesis was detected, B lymphocytes synthesized IgM upon stimulation with IL2 alone. Analysis of mRNA levels was performed on the cells of this latter patient after culture without or with IL2. In the presence of IL2 we observed a strong enhancement of C mu gene expression associated with an increase of the ratio between the secreted form and the membrane-bound form of mu mRNA. In contrast IL2 induced only a marginal enhancement of J chain mRNA. Thus, terminal B cell differentiation of selected monoclonal B cells can be obtained in the absence of DNA synthesis and IL2 alone can mediate this process. Moreover, IL2 can act at selective steps of the molecular events associated with IgM production. These results document the multiple effects of a given IL on the events leading to antibody production and strongly suggest that they can be conditioned by the maturation stage of a given responding cell.

Interferon-alpha can synergize with interleukin 2 for human in vitro antibody response

We tested the effect of interferon (IFN)-alpha on the specific anti-2,4,6-trinitrophenyl (TNP) response induced by TNP-conjugated polyacrylamide beads in cultures of purified human B cells. IFN-alpha alone had no effect. Interleukin 2 (IL2) alone had a restorative effect which could be considerably (10X) enhanced by IFN-alpha. This reflected a true synergy most apparent with IL2 concentrations of 10 U/ml and IFN-alpha concentrations of 10(3)-10(5) U/ml. The highest concentrations of IFN-alpha were not inhibitory. In contrast, IFN-alpha did not enhance the effect of an IL2-free T cell-derived supernatant able to support the B cell differentiation. Sequential incubations showed that IFN-alpha acted earlier than IL2 on B cell response. The effect of IFN-alpha was dependent on an efficient interaction between IL2 and its receptor which could be inhibited by a monoclonal antibody toward the CD25 antigen. Thus, IFN-alpha can positively interact with a well defined interleukin, IL2, at a pre or post receptor level to potentiate antibody response.