Retinoic acid induces the differentiation of B cell hybridomas from patients with common variable immunodeficiency

Vitamin A dietary supplementation reduces the mortality of velogenic Newcastle disease significantly in cockerels

This project was undertaken to find ways of reducing mortalities and economic losses due to velogenic Newcastle disease (VND) in areas where the disease is enzootic. Four groups of cockerels of 44 birds each were used for this experiment. The birds in groups 1 and 2 received no dietary vitamin A supplementation, whereas groups 3 and 4 received 300 iu and 600 iu of vitamin A per kilogram of commercial feed, respectively, from 1 week of age till the end of the experiment. At 6 weeks of age, the birds in groups 2, 3 and 4 were inoculated intraocularly with a VND virus (duck/Nigeria/Plateau/Kuru/113/1991). The birds in Group 1 were given phosphate-buffered saline intraocularly. Clinical signs appeared in Group 2 birds on day 3 PI and in groups 3 and 4 on day 5 PI. The clinical signs included a drop in feed and water consumption, depression, diarrhoea, torticollis and paralysis in all the infected groups. The average body weights of all groups were significantly different from one another on day 14 PI with Group 2 birds having the lowest body weight. Mortalities were highest in Group 2 birds (0%, 93.18%, 72.73% and 56.82% in groups 1, 2, 3 and 4 respectively). The antibody response in all the groups was significantly different from one another on days 14 and 21 PI. Group 2 birds had the lowest titres on those 2 days and showed more severe atrophy of the bursa, spleen, thymus and fibrin deposition in the spleen and thymus than the birds in groups 3 and 4. The above observations show that vitamin A dietary supplementation delayed the onset of clinical signs and significantly reduced body weight loss, atrophy of the bursa, spleen and thymus, and mortalities by 36%. It also significantly potentiated haemagglutination inhibition antibody response.

Research resource: Comparative nuclear receptor atlas: basal and activated peritoneal B-1 and B-2 cells

Naïve murine B cells are typically divided into three subsets based on functional and phenotypic characteristics: innate-like B-1 and marginal zone B cells vs. adaptive B-2 cells, also known as follicular or conventional B cells. B-1 cells, the innate-immune-like component of the B cell lineage are the primary source of natural antibodies and have been shown to modulate autoimmune diseases, human B-cell leukemias, and inflammatory disorders such as atherosclerosis. On the other hand, B-2 cells are the principal mediators of the adaptive humoral immune response and represent an important pharmacological target for various conditions including rheumatoid arthritis, lupus erythematosus, and lymphomas. Using the resources of the Nuclear Receptor Signaling Atlas program, we used quantitative real-time PCR to assess the complement of the 49 murine nuclear receptor superfamily expressed in quiescent and toll-like receptor (TLR)-stimulated peritoneal B-1 and B-2 cells. We report the expression of 24 nuclear receptors in basal B-1 cells and 25 nuclear receptors in basal B-2 cells, with, in some cases, dramatic changes in response to TLR 4 or TLR 2/1 stimulation. Comparative nuclear receptor profiling between B-1 and peritoneal B-2 cells reveals a highly concordant expression pattern, albeit at quantitatively dissimilar levels. We also found that splenic B cells express 23 nuclear receptors. This catalog of nuclear receptor expression in B-1 and B-2 cells provides data to be used to better understand the specific roles of nuclear receptors in B cell function, chronic inflammation, and autoimmune disease.

Peroxisome proliferator-activated receptor gamma ligands enhance human B cell antibody production and differentiation

Protective humoral immune responses critically depend on the optimal differentiation of B cells into Ab-secreting cells. Because of the important role of Abs in fighting infections and in successful vaccination, it is imperative to identify mediators that control B cell differentiation. Activation of B cells through TLR9 by CpG-DNA induces plasma cell differentiation and Ab production. Herein, we examined the role of the peroxisome proliferator-activated receptor (PPAR)gamma/RXRalpha pathway on human B cell differentiation. We demonstrated that activated B cells up-regulate their expression of PPARgamma. We also show that nanomolar levels of natural (15-deoxy-Delta(12,14)-prostaglandin J(2)) or synthetic (rosiglitazone) PPARgamma ligands enhanced B cell proliferation and significantly stimulated plasma cell differentiation and Ab production. Moreover, the addition of GW9662, a specific PPARgamma antagonist, abolished these effects. Retinoid X receptor (RXR) is the binding partner for PPARgamma and is required to produce an active transcriptional complex. The simultaneous addition of nanomolar concentrations of the RXRalpha ligand (9-cis-retinoic acid) and PPARgamma ligands to CpG-activated B cells resulted in additive effects on B cell proliferation, plasma cell differentiation, and Ab production. Furthermore, PPARgamma ligands alone or combined with 9-cis-retinoic acid enhanced CpG-induced expression of Cox-2 and the plasma cell transcription factor BLIMP-1. Induction of these important regulators of B cell differentiation provides a possible mechanism for the B cell-enhancing effects of PPARgamma ligands. These new findings indicate that low doses of PPARgamma/RXRalpha ligands could be used as a new type of adjuvant to stimulate Ab production.

Vitamin A potentiates CpG-mediated memory B-cell proliferation and differentiation: involvement of early activation of p38MAPK

Foreign CpG-DNA from viruses and bacteria can activate memory B cells through binding to toll-like receptor 9, and this pathway has been hypothesized to be involved in the continuous activation of memory B cells ensuring life-long humoral immunity. In this study, we demonstrate that retinoic acid (RA) is a potent coactivator of this pathway in human B cells. RA enhanced the CpG-mediated proliferation of CD27(+) memory B cells, and the proliferative response was accompanied by increased immunoglobulin (Ig) secretion indicative of plasma-cell formation. The RA-induced proliferation was preceded by enhanced expression of cyclin D3, and both the expression of cyclin D3 and the induced Ig secretion were found to be dependent on IL-10. Of importance, RA increased the CpG-induced phosphorylation of ERK1/2, p38MAPK, and IkappaB as early as 30 minutes after stimulation. By using specific inhibitors, all the RA-mediated events, including proliferation, cyclin D3 expression, IL-10 secretion, and Ig secretion, were shown to be dependent on p38MAPK. Hence, we propose that RA can strengthen humoral immunity by promoting CpG-mediated stimulation of CD27(+) B cells via activation of p38MAPK resulting in increased proliferation and differentiation to Ig-secreting plasma cells.

Therapeutic strategies in common variable immunodeficiency

The treatment of common variable immunodeficiency (CVID) is currently based on the early recognition of the condition and replacement immunoglobulin combined with prompt treatment of infections and complications. The route of administration, dose and frequency of administration of immunoglobulin still vary between centres and countries. Other interventions aimed at overcoming the immunological defects in CVID such as interleukin-2 therapy are being studied but there is as yet insufficient evidence to support their routine use. The treatment of complications such as suppurative lung disease uses principles broadly similar to those used for cystic fibrosis, whereas the granulomatous complications involving the lungs and other organ systems are in need of much more research to define optimum therapies.

In vitro effects of retinoids on the proliferation and differentiation features of Epstein-Barr virus-immortalized B lymphocytes

Retinoids have been shown to be effective in the chemoprevention and treatment of certain human malignancies. In this review, we will summarize our recent results concerning the effects of retinoids on the proliferation and differentiation of Epstein-Barr virus (EBV)-immortalized lymphoblastoid B-cell lines (LCLs), an in vitro model of EBV-related lymphoproliferative disorders arising in immunosuppressed hosts. Retinoids proved to be powerful inhibitors of the proliferation of EBV-infected LCLs in vitro, with 13-cis-retinoic acid (RA), all-trans-RA, and 9-cis-RA being the most effective compounds. Of note, retinoid-induced growth arrest in vitro appears irreversible at drug concentrations (10(-6) mol/L) which may be reached in man after oral systemic therapy. The antiproliferative activity exerted by retinoids on LCLs is a generalized phenomenon usually associated with a progressive accumulation in G0/G1 phases of treated cells. The strong upregulation of p27Kip1 invariably observed in cells exposed to retinoids may contribute to the decreased number of cycling cells, probably by inhibiting the transition from the G1 to S phase. Moreover, we obtained evidence indicating that the antiproliferative effects of retinoids are not dependent on the induction of terminal differentiation of EBV-immortalized B lymphocytes. In fact, the modifications induced by retinoids relative to LCL morphology, phenotype (downregulation of CD19, HLA-DR, and s-Ig, and upregulation of CD38 and c-Ig), and IgM production were highly variable among the lines tested and often only slightly relevant. Finally, the antiproliferative activity exerted by retinoids on LCLs is not mediated by a direct modulation of viral latent antigens, since EBNA-2 and LMP- downregulation was a late event detected only in some cell lines. These results indicate that retinoids may be useful in the medical treatment of EBV-related lymphoproliferative disorders of immunosuppressed patients, particularly in the earlier phases of these diseases.

Retinoid regulation of interleukin-2 receptors on human T-cells

The ability of retinoids to regulate interleukin-2 receptor (IL-2R) levels on human T-cells may play a fundamental role in the immunomodulating effects of these compounds. As a cell line model for studying this phenomenon, we tested the effects of retinoic acid (RA) on the expression of IL-2Ralpha and IL-2Rbeta in Hut78 cells, a mature T-cell line derived from a Sezary T-cell leukemia. Our results demonstrated 4- to 20-fold increases in the surface expression and mRNA levels of both of these receptor components at RA concentrations starting at 10(-10) M with maximal induction at 1 microM RA. RA-induced upregulation of IL-2Rbeta was found to be transcriptionally mediated in a protein-synthesis-independent fashion; however, activation of the IL-2Rbeta promoter could not be demonstrated in transient transfection experiments utilizing reporter gene constructs containing all currently known regulatory elements of the IL-2Rbeta promoter. Enhancement of IL-2Ralpha/beta by RA was accompanied by upregulation of the expression of CD38, CD69, CD45RO, and HLA-DR, surface molecules known to be associated with T-cell activation. Parallel effects were induced by RA on T-blasts generated from primary human lymphocytes suggesting the physiologic relevance of the Hut78 cell line model. Taken together, our findings demonstrate the ability of RA to upregulate IL-2R expression and enhance the activation state of Hut78 cells. The dramatic enhancing ability of RA on IL-2Rbeta expression does not appear to be mediated through interaction with currently defined regions of the IL-2Rbeta promoter.

The effects of retinoic acid on immunoglobulin synthesis: role of interleukin 6

Retinoic acid (RA) and its parent compound, retinol (ROH, vitamin A), have been recognized as important immunopotentiating agents. Previous studies from our laboratory have demonstrated that RA can augment formalin-treated Staphylococcus aureus (SAC)-stimulated immunoglobulin (Ig) synthesis of cord blood mononuclear cells (CBMC). To determine the mechanism(s) by which RA modulates Ig synthesis, we studied the effects of RA on B cells and cytokine production. The addition of RA (10(-5) to 10(-10) M) to Epstein-Barr virus (EBV)-transformed B-cell clones derived from either adult or cord blood B cells augmented Ig secretion twofold. In contrast, cell proliferation was inhibited as measured by 3H-thymidine incorporation. We evaluated two cytokines known to be constitutively produced by EBV cell lines, IL-1 and IL-6. While RA had no effect on IL-1 production, IL-6 synthesis was greatly enhanced (20- to 45-fold), which was also reflected by an increase in steady-state mRNA levels for IL-6 but not TNF-alpha or TGF-beta on Northern blot analysis. Polyclonal rabbit anti-IL-6 antibodies were used to block the augmenting effects of RA on Ig synthesis of adenoidal B cells. RA-induced augmentation in IgG and IgA synthesis was blocked 58 and 29%, respectively, by anti-IL-6 antibodies. These studies suggest that the enhancing effects of RA on Ig synthesis are mediated, at least in part, by the autocrine or paracrine effects of IL-6 on B-cell differentiation.

Human antibody variable region gene usage in HIV-1 infection

Human antibody variable region gene usage during human immunodeficiency virus type 1 (HIV-1) infection is examined in the following review, and several hypotheses are presented to account for the distinct patterns of antibody gene expression associated with infection. Evidence supporting qualitatively biased antibody gene expression has been derived from analysis of the human humoral immune response by isoelectric focusing (IEF) and serological and molecular studies of immunoglobulin (Ig) from different lymphoid compartments of HIV-1-infected patients. Preferential usage of heavy-chain variable region (VH) gene families 1 and 4 is supported by serological studies of serum Ig and molecular characterization of anti-HIV-1 human monoclonal antibodies derived from infected patients. Negative biases against VH3 family gene usage are detected by polymerase chain reaction (PCR) studies of peripheral blood lymphocytes from AIDS patients but not by combinatorial phage display library techniques. Biased antibody gene usage and expression during HIV-1 infection may be related to HIV-1 pathogenesis by limiting the available HIV-1 neutralizing repertoire. Further molecular characterization of anti-HIV-1 antibodies and in vivo expression of V-region genes during HIV-1 infection should provide important information regarding antibody gene expression and its relationship to HIV-1 pathogenesis.

Intrinsic defect in B cells of patients with hyper-immunoglobulin M syndrome

We challenge the theory that the CD40-CD40 ligand is the only explanation for X-linked immunodeficiency in patients with hyper-immunoglobulin M (IgM) syndrome (HIGM1), and we demonstrate an intrinsic defect in the patients' B cells. Patients with HIGM1 have a defective CD40 ligand on their activated T-helper cells; therefore, they cannot receive signals for isotype switching when the cells are activated by T cell-dependent antigens. We activated mononuclear cells from three patients with HIGM1 and from three healthy blood donors with T cell-independent mitogens and studied their proliferative responses and Ig secretion. Normal murine plasma membrane fragments were implanted into peripheral blood mononuclear cells, and the cells were activated with Staphylococcus aureus Cowan I, pokeweed mitogen, and lipopolysaccharide. This implantation significantly augmented the proliferative responses to the mitogens in two patients. However, it augmented IGM secretion in response to B-cell mitogens in only one patient. No IgG or IgA response could be detected in the implanted mononuclear cells that originated from patients with HIGM1, unlike implanted mononuclear cells from healthy donors, which responded by IgM, IgG, and IgA antibody secretion following their stimulation with B-cell mitogens. The data suggest that the B cells of patients with HIGM1 possess an additional defect which prevents Ig isotype switching in response to T cell-independent mitogens. This defect is not located in the membrane receptors or within the membrane enzymes.

Retinoic acid induces translocation of protein kinase C (PKC) and activation of nuclear PKC (nPKC) in rat splenocytes

Retinoic acid (RA), a vitamin A metabolite, has marked effects on growth of normal and malignant cells; however, the exact mechanism of action remains unclear. The effect of two RA analogs, 13-cis-RA and all-trans-RA, on transmembrane signalling processes was investigated in rat splenocytes. Treatment of rat splenic cells with these retinoic acid analogs resulted in translocation of protein kinase C (PKC) from the cytosol to the membrane. Previous studies have described nuclear RA receptors (RARs and RXRs) for several species and the biologic activity of RA has been shown to be mediated by specific interaction with these nuclear receptors. Thus, activation of nuclear pool(s) of protein kinase C (nPKC) by RA analogs was also studied. Rat splenocyte nuclei pure by enzymatic and electron microscope criteria demonstrated a biphasic pattern of bell-shaped curves for both cis- and trans-RA with maximum statistically significant peak of phosphate incorporation into endogenous substrates at 10(-16) M cis-RA and 10(-16)-10(-17) M trans-RA. A monoclonal antibody to PKC and the PKC inhibitors, H-7, sphingosine, and staurosporine, blocked the RA-stimulated nuclear phosphorylation. The ability of RA to activate cell membrane PKC resulting in an increase in particulate PKC activity correlates well with the activation of nPKC since the particulate fraction would include nuclear enzyme systems. This ability of RA to activate nPKC and possibly affect the growth status of a cell may provide a missing link to our understanding of the cellular sites of action for this vitamin.

Transcriptional regulation by retinoic acid of interleukin-2 alpha receptors in human B cells

In this study, we demonstrated that retinoic acid (RA) up-regulated interleukin-2 receptor-alpha (IL-2R alpha) expression on two human B-cell lines, IE8.6 and SKW6.4. Deleted forms of the human IL-2R alpha promoter linked to the bacterial chloramphenicol acetyltransferase reporter gene were transfected into IE8.6 cells in order to define RA-responsive regulatory domains. Experiments using the -1.6 kb construct, which contains all known regulatory regions in the IL-2R alpha promoter, indicated that RA could induce IL-2R alpha promoter activity. The basal activity of the -471 construct was initially low, but was markedly enhanced by the addition of RA. Deletion of promoter sequences between -471 and -317 resulted in a significant augmentation of basal promoter activity and abolished promoter induction by RA. This finding revealed a requirement for sequences 5' of base -317 for RA-induced promoter activation, raising the possibility of the presence of both a RA response element and a negative regulatory element (NRE) upstream of base -317. Transfection studies with internal deletion mutants with the putative NRE removed resulted in increases in basal promoter activity and unresponsiveness to RA similar to the -317 construct. In contrast, an internal deletion mutant with the NRE intact had low basal activity and was inducible by RA similar to the -471 construct. Taken together, our results suggested that RA-induced activation of the IL-2R alpha promoter was through changes in the function of a NRE present between bases -400 and -368. This 31-base pair element may interact with an adjacent RA-responsive regulatory site as well as being responsible for down-regulation of basal IL-2R alpha expression under certain conditions.

Long-term administration of 13-cis retinoic acid in common variable immunodeficiency: circulating interleukin-6 levels, B-cell surface molecule display, and in vitro and in vivo B-cell antibody production

We have previously shown that retinoids can induce differentiation of B cells in vitro as well as in vivo in patients with common variable immunodeficiency (CVI). While changes were observed over 1 week when retinoic acid (RA) was added to CVI hybridoma cells in vitro, maturation of the patients' B-cell compartment in vivo occurred only after 4 months of drug administration. We have now performed a 64-week open trial of oral 13-cis RA in five patients to see if prolonged treatment would result in continued improvement in their humoral immune compartment. In this trial, drug was given for 32 weeks followed by a 32-week wash-out period. During the treatment, the patients showed changes in a variety of parameters indicating an alteration towards normal of their humoral immune systems. This change included a fall in the elevated circulating interleukin-6 (IL-6) levels, a more normal display of B-cell surface markers (L-selectin and CD20), a decrease in B-cell size, and improved in vitro and in vivo B-cell function. In order to determine if VH gene use was affected by the retinoid treatment, VH gene expression in the CVI patients was characterized. Results showed an unusual predominance of non-mutated VH gene sequences, representative of cells that are recent bone marrow emigrants. While no common pattern of change occurred in VH gene segment use in the patients while on retinoid therapy, large-scale (> 10-fold) changes in the expression of these genes were observed in each individual over time. Taken together, these results provide multiple lines of evidence that 13-cis RA promotes maturation of B cells in patients with CVI. However, the effect appears to be partial, such that stimuli in addition to 13-cis RA will be necessary to provide for further B-cell differentiation in order to achieve normalization of humoral immunity.

Retinoic acid induces changes in c-fgr proto-oncogene mRNA levels in Burkitt's lymphoma cells

The c-fgr proto-oncogene is expressed in Burkitt's lymphoma (BL) cell and cell lines derived from them. When Epstein-Barr virus (EBV)-negative BL cell lines that contain low levels of c-fgr mRNA are infected with EBV, transcription of the c-fgr gene is further induced. In this paper we show that treatment of EBV-negative and EBV-positive BL cell lines with all-trans retinoic acid also stimulates an increase in c-fgr mRNA levels, varying between 2- and 13-fold depending on the cell line. An increase is detectable 12 to 48 h after treatment, depending on the cell line, suggesting that the c-fgr gene is not regulated directly by retinoic acid but responds to other retinoic acid-induced changes in the cell. We also show that treatment of BL cell lines with all-trans retinoic acid either results in a dose-dependent decrease in growth rate, or has no effect on growth, depending on the cell line. It has previously been suggested that the c-fgr gene product might have a role in regulating the growth of BL cells, since treatment of the EBV-positive BL cell line Daudi with alpha-interferon results in a decrease in c-fgr mRNA levels followed by a decrease in growth rate. Our data indicate that there is no general correlation between c-fgr mRNA levels and growth rate in BL cells and so argue against a role for the c-fgr gene product in growth regulation in these cells.

B cells from subjects with CVI can be driven to Ig production in response to CD40 stimulation

The majority of patients with common variable immunodeficiency (CVI) have low to normal numbers of membrane Ig-bearing B cells; yet these cells fail to differentiate in vivo resulting in hypogammaglobulinemia. We have suggested that the differentiation failure of CVI B cells is related to a failure to respond appropriately to signals involved in terminal B cell differentiation as most CVI subjects' cells undergo activation and proliferation normally. Whether this failure relates to a direct "intrinsic" defect in the B cells or is secondary to a lack of appropriate T cell or other influences in vivo is uncertain. We have previously reported that the majority of patients with CVI have elevated circulating levels of IL-6. We now show that the IL-6 produced by these patients is functionally normal. Additionally, the display of IL-6 receptors on in vitro stimulated CVI B cells is normal. However, we found that the patients' cells do not make IgE in response to an IL-6/T-cell-dependent differentiation pathway employing exogenous interleukin-4 (IL-4). The failure to respond in the IL-6-dependent system could not be overcome by exogenous IL-6 or varying doses of IL-4. In contrast, when stimulated by CD40 plus IL-4 in a differentiation pathway that does not require IL-6, B cells from CVI patients were stimulated to produce IgE. These findings, along with our earlier data showing that 13-cis-retinoic acid can drive maturation in CVI patients, strengthen the concept that B cells in patients with CVI have the potential for terminal differentiation but do not appear to achieve this in vitro or in vivo through a polyclonal Ig differentiation pathway that employs IL-6 as one of its maturation signals.

The second century of the antibody. Molecular perspectives in regulation, pathophysiology, and therapeutic applications

The modern age of immunology began in 1890 with the discovery of antibodies as a major component of protective immunity. The 2nd century of the antibody begins with a focus on the molecular physiology and pathophysiology of immunoglobulin production. Numerous human variable-region antibody genes have been identified through advances in molecular cloning and anti-variable-region monoclonal antibodies. Some of these variable-region genes are now known to be involved in specific stages of B-lymphocyte differentiation and immune development. This connection has yielded new insights into the pathogenesis of immune dyscrasias and lymphoid neoplasia; common variable immunodeficiency and cryoglobulinemia are highlighted here. The molecular regulation of immunoglobulin expression suggests new targets for pathogenesis and clinical intervention. Finally, genetically engineered antibodies offer novel opportunities for diagnostic and therapeutic applications.

13-cis retinoic acid enhances in vivo B-lymphocyte differentiation in patients with common variable immunodeficiency

Retinoic acid (RA) has been demonstrated to drive both phenotypic and functional in vitro differentiation of B cell hybridomas from patients with common variable immunodeficiency (CVI) who manifest an "intrinsic" defect in terminal B cell differentiation (J Exp Med 1988;168: 55-71). Therefore, we conducted an open trial to determine the effects of oral 13-cis RA (0.5 mg/kg/day; 12 weeks receiving and 12 weeks without drug) on in vivo B cell differentiation in subjects with CVI. At various times before, during, and after drug administration, patients' B cells were tested for changes in cell-surface phenotype and in vitro immunoglobulin production in response to recombinant cytokines. Before 13-cis RA, all patients had decreased Leu-8 coexpression on CD20+ cells. Seven of eight subjects demonstrated "normalization" of this phenotype after 8 to 16 weeks of 13-cis RA administration. Patients whose B cells demonstrated more than normal CD20 display also had a fall toward normal in this parameter. These effects persisted for 6 to 12 weeks after drug was stopped. It appears that 13-cis RA drives B cells of patients with CVI to express a more differentiated cell-surface phenotype and may promote functional differentiation in some patients.

Expression of immunoglobulin genes in common variable immunodeficiency

Five common variable immunodeficiency (CVI) patients were analyzed for expression of immunoglobulin (Ig) genes. In the pokeweed mitogen (PWM)-induced Ig-production assay, the combination of T and B cells showed that all patients' T cells had normal helper functions and all patients' B cells had profound defects. The defective B-cell maturation stages based on their Ig gene expression patterns were variable. One of five patients showed normal mu-chain gene expression and nearly normal IgM production, but neither IgG nor IgA production, which suggested that this patient's B-cell defects might lie on a mu- to gamma or mu- to alpha class-switch stage. B cells in another patient showed low mu-chain gene expression and low IgM production, but an Ig enhancer region, which is an important region for expression of Ig genes, was intact. Thus, this patient might have a transacting factor defect which interacts with the Ig enhancer region. The other three patients showed no mu-chain gene expression and no IgM production. Thus, their B-cell defects lay on the B-cell maturation stage, similar to X-linked agammaglobulinemia. These results showed that primary B-cell defects in CVI occurred at several B-cell differentiation stages, which could be recognized by expression of Ig genes.

The effects of retinoic acid on immunoglobulin synthesis by human cord blood mononuclear cells

Derivatives of vitamin A have attracted considerable attention as agents which have immune potentiating properties and possibly tumor-suppressive effects. Recent investigations have shown that retinoic acid (RA) can augment immunoglobulin production of B-cell hybridomas from patients with immune deficiency. In this study we examined the ability of RA to modify the mitogen-induced polyclonal immunoglobulin synthesis of cord blood mononuclear cells (CBMC). RA in concentrations ranging from 10(-5) to 10(-7) M augmented IgM synthesis of CBMC in response to formalinized Cowans I strain Staphylococcus aureus (SAC) up to 45.6-fold which was greater at suboptimal responses to SAC. There were no changes in IgG or IgA synthesis and minimal effects on SAC-induced proliferative responses. RA did not produce similar changes in IgM synthesis of SAC-stimulated adult peripheral blood mononuclear cells (PBMC), and RA had no effect on the immunoglobulin synthesis of Epstein-Barr virus (EBV)-stimulated CBMC or adult PBMC. Time course studies showed that peak enhancement occurred when RA was added between 4 and 24 hr after culture initiation and required prior activation by SAC for augmentation of IgM synthesis. Cell separation experiments showed that prior incubation (18 hr) of an enriched T-cell fraction with RA enhanced the IgM synthesis of a T-cell-depleted B-cell fraction. These experiments and the findings that RA-induced augmentation of IgM production in response to SAC, but not to EBV suggest that the immunoregulatory effects of RA may be mediated by either T cells or T-cell products. Further studies will be necessary to understand the mechanism by which RA augments IgM synthesis of CBMC.

Differential effects of retinoids on pokeweed mitogen induced B-cell proliferation vs immunoglobulin synthesis

The effects of three retinoids, all-trans-retinoic acid (RA), 13-cis-retinoic acid (cRA), and N-(4-hydroxyphenyl) retinamide (4-HPR) on mouse splenocyte responses to pokeweed mitogen (PWM) and Escherichia coli lipopolysaccharide (LPS) in vitro were evaluated. All three retinoids caused a dose dependent increase in the proliferative response to PWM. The retinoids hierarchy of efficacy based on potentiation of PWM-induced splenocyte proliferation was RA greater than cRA greater than 4-HPR. 13-cis-retinoic acid and 4-HPR also resulted in significant increases in Ig secretion in response to PWM. However, RA did not produce a significant increase in secretion compared with cells treated with PWM alone. The efficacy hierarchy of retinoids ability to potentiate Ig secretion was 4-HPR greater than cRA greater than RA. All three compounds did not affect Ig secretion from LPS-stimulated splenocytes and produced dose dependent decreases in proliferation. Both inhibition of LPS-induced proliferation and potentiation of PWM-induced proliferation were maximal when the retinoids were added during the first hour of culture. These results indicate that retinoids have a differential effect on Ig secretion and B-cell proliferation based on structural differences of the retinoids. Potentiation of proliferation and Ig secretion are both T-cell dependent and could be a result of increased lymphokine synthesis by the T-cells or increased responsiveness to the effects of the T-cell produced lymphokines.

Effects of 13-cis retinoic acid therapy on human antibody responses to defined protein antigens

We have evaluated the in vivo effects of 13-cis retinoic acid (13-cis RA) on human antibody responses to immunization with tetanus toxoid (TT) and keyhole limpet hemocyanin (KLH). Subjects with severe cystic acne were immunized with suboptimal doses (10 micrograms) of KLH 7 d and 3 months after starting retinoid therapy (13-cis RA, 1 mg/kg/day for 4 mo). A standard booster immunization with TT was given along with the initial KLH sensitization. A control group of acne patients received identical immunization regimens, but no 13-cis RA. Plasma retinoid levels were evaluated by reverse-phase HPLC and confirmed that blood-level concentrations of 13-cis RA and metabolites in these acne patients reached values previously demonstrated to be immunomodulatory in vitro. The retinoid had no effect on responses to TT as reflected by the characteristics of increased anti-TT IgG levels or the isotype distribution of the antibody. In contrast, the anti-KLH response was significantly enhanced in the 13-cis-RA-treated group. Whereas anti-KLH antibody was detected in only 4 of 13 control subjects after the secondary immunization, 10 of 13 retinoid-treated subjects had measurable levels of anti-KLH IgG (p less than 0.05). Among the responders, no differences were noted in the isotype distribution of anti-KLH antibody. These results showing enhanced anti-KLH responses induced by 13-cis RA therapy represent the first demonstration in humans that in vivo administration of a retinoid can modulate antigen-specific immune responses.

Retinoids increase perinatal spinal cord neuronal survival and astroglial differentiation

In this report we demonstrate that retinol and retinoic acid (RA) increase the survival and morphological differentiation of rat spinal cord neurons in vitro. Micromolar amounts of retinol and RA increased the number of surviving neurons by 2- to 3-fold and affected neuritic density resulting in increased secondary and tertiary processes compared to untreated sister cultures. A marked morphological differentiation of the astrocyte population in conjunction with an antiproliferative effect in the presence of retinoids were apparent. These trophic effects occurred mainly after 5 days in vitro, a time that corresponds to the time of birth in vivo. Retinoic acid exerted a direct trophic effect on spinal cord neurons in the absence of glial cells while retinol lost its effectiveness. Metabolic labeling suggested that retinol is converted to the biologically active RA within astrocytes but not in neurons. Taken together, our results have demonstrated direct trophic effects of RA on spinal cord neurons and have suggested another role for astrocytes in the maintenance of normal neural physiology by regulating RA concentrations through the oxidation of retinol.

The role of lymphokines in common variable hypogammaglobulinemia

Common variable (acquired) hypogammaglobulinemia (CVH) is a rare primary immunodeficiency disease of great interest as an immunological model of defects in antibody production. In this article, Gavin Spickett and John Farrant discuss evidence of abnormalities in lymphokine production and responses in the generation of the functional failure. It is not yet clear whether the B cell is intrinsically abnormal or lacks appropriate signals, but the block appears to occur in the differentiation phase of B cells, since membrane (but not secreted) IgG is made. Some T-cell defects also occur in this disease. The cause of CVH is unknown, although a viral aetiology has been suggested. Better understanding of lymphokine networks may allow the provision of specific signals to overcome the block in antibody production.