The effects of retinol on in vitro immunoglobulin synthesis by cord blood and adult peripheral blood mononuclear cells

Effectiveness of vitamin A acetate for enhancing the production of lung cancer specific monoclonal antibodies

The antibody productivity of the human-human hybridoma cell line AE6, which produces the lung cancer specific human monoclonal antibody AE6F4, was enhanced fourfold upon stimulation with 1 mug/ml of vitamin A acetate for one day. The enhancement lasted for about two weeks, and could be repeated by another stimulation with vitamin A acetate. The enhancing effect of vitamin A acetate was influenced by the cell density. Enhancement was clearly observed when the cell density was under 10(6) cells/ml. However, when the cell density was over 10(7) cells/ml, enhancement was observed weakly or not at all. Although the enhancing effect of vitamin A acetate is not unique to AE6 cells, not all human-human hybridoma cell lines show increased productivity upon VA acetate stimulation. This study suggests that the response to vitamin A acetate may be related to the properties of a particular fusion partner which the hybridoma cell inherits. The efficacy of vitamin A acetate for production of human monoclonal antibodies using human-human hybridomas is discussed.

All-trans-retinoic acid accelerates the differentiation of human B lymphocytes maturing into plasma cells

There is a growing body of evidences suggesting the important role of vitamin A for the optimal maintenance and functioning of immune system. It is now well established that retinoic acid (RA), a product of oxidative metabolism of vitamin A, is the most active vitamin A derivative physiologically. In this study, we examined the role of RA in B cell maturation in T cell-dependent activation pathway. RA enhanced the immunoglobulin synthesis by tonsillar B cells in anti-CD40 plus IL-10-mediated culture system. When the kinetics of B cells with different phenotypic characteristics were monitored during 9 days culture period by flow cytometric analysis, it displayed the increase of the B cells with plasma cell phenotype (CD38+/CD20-/IgD-) in the presence of RA. As resting B cells from tonsil expressed mRNA of the RA receptors alpha, beta, gamma and RXRalpha by reverse transcriptase-polymerase chain reaction, it is certain that RA effect is mediated by RA receptors. Taken together, this study showed that retinoic acid could accelerate the differentiation of B cells maturing into antibody producing cells.

Analysis of mouse retinal dehydrogenase type 2 promoter and expression

The mouse RALDH2 gene spans >50 kb, has a structure similar to that of human class 1 aldehyde dehydrogenase genes, and localizes to the central region of chromosome 9 by single-strand polymorphism analysis. Expression of mouse RALDH2 was detected in testis, lung, brain, and heart (Northern blot) and in liver and kidney (RNase protection assays). Expression was not detected by RNase protection assay in testis of vitamin A-deficient rats, and all-trans-retinoic acid dosing did not increase expression in vitamin A-deficient rat testis. A 2.3-kb section of the gene 5' to the transcription start site included neither retinoic acid nor retinoid X response elements, but included TATA and CCAAT motifs and AP, AHR, CREB, ER, Ets, and SREBP sites. The promoter initiated transcription of a luciferase reporter in human embryonic kidney cells (EBNA) and mouse Leydig- (TM3) and Sertoli-derived (TM4) cell lines, but neither all-trans-retinoic acid nor 9-cis-retinoic acid affected reporter transcription. These data suggest that relatively weak RALDH2 expression in vitamin A-deficient testis reflects vastly decreased numbers of germ cells, the major site of expression.

Simultaneous vitamin A administration at routine immunization contact enhances antibody response to diphtheria vaccine in infants younger than six months

A randomized, double-blind, placebo-controlled trial was conducted to evaluate the effect of simultaneous vitamin A supplementation and diphtheria, pertussis and tetanus (DPT) vaccination on the antibody levels. Infants aged 6-17 wk (n = 56) were randomly given 15 mg oral vitamin A or placebo at the time of their DPT immunization. Three such doses were given at monthly intervals. Immunoglobulin (Ig) G antibodies to diphtheria, pertussis and tetanus were assayed on enrollment and 1 mo after the third dose. Baseline antibody concentrations to diphtheria, pertussis and tetanus did not differ between the vitamin A-supplemented and placebo-treated groups. The postdose antibody to diphtheria level was significantly greater in the vitamin A than in the placebo-treated group. The geometric mean +/- SEM antibody levels (mg/L) were 22.9 +/- 1.2 and 11.0 +/- 1.3 in the vitamin A and placebo groups, respectively (P = 0.029). The postsupplementation concentrations of antibodies to pertussis and tetanus did not differ between the two groups. These results suggest that antibody response to diphtheria vaccination was potentiated by simultaneous vitamin A administration and DPT immunization.

Retinoic acid: its biosynthesis and metabolism

This article presents a model that integrates the functions of retinoid-binding proteins with retinoid metabolism. One of these proteins, the widely expressed (throughout retinoid target tissues and in all vertebrates) and highly conserved cellular retinol-binding protein (CRBP), sequesters retinol in an internal binding pocket that segregates it from the intracellular milieu. The CRBP-retinol complex appears to be the quantitatively major form of retinol in vivo, and may protect the promiscuous substrate from nonenzymatic degradation and/or non-specific enzymes. For example, at least seven types of dehydrogenases catalyze retinal synthesis from unbound retinol in vitro (NAD+ vs. NADP+ dependent, cytosolic vs. microsomal, short-chain dehydrogenases/reductases vs. medium-chain alcohol dehydrogenases). But only a fraction of these (some of the short-chain de-hydrogenases/reductases) have the fascinating additional ability of catalyzing retinal synthesis from CRBP-bound retinol as well. Similarly, CRBP and/or other retinoid-binding proteins function in the synthesis of retinal esters, the reduction of retinal generated from intestinal beta-carotene metabolism, and retinoic acid metabolism. The discussion details the evidence supporting an integrated model of retinoid-binding protein/metabolism. Also addressed are retinoid-androgen interactions and evidence incompatible with ethanol causing fetal alcohol syndrome by competing directly with retinol dehydrogenation to impair retinoic acid biosynthesis.

Interactions of retinoid binding proteins and enzymes in retinoid metabolism

Naturally occurring retinoids (vitamin A or retinol and its active metabolites) are vital for vision, controlling the differentiation program of epithelial cells in the digestive tract and respiratory system, skin, bone, the nervous system, the immune system, and for hematopoiesis. Retinoids are essential for growth, reproduction (conception and embryonic development), and resistance to and recovery from infection. The functions of retinoids in the embryo begin soon after conception and continue throughout the lifespan of all vertebrates. Both naturally occurring and synthetic retinoids are used in the therapy of various skin diseases, especially acne, for augmenting the treatment of diabetes, and as cancer chemopreventive agents. Retinol metabolites serve as ligands that activate specific transcription factors in the superfamily of steroid/retinoid/thyroid/vitamin D/orphan receptors and thereby control gene expression. Additionally, retinoids may also function through non-genomic actions. Various retinoid binding proteins serve as partners in retinoid function. These binding proteins show high specificity and affinity for specific retinoids and seem to control retinoid metabolism in vivo qualitatively and quantitatively by reducing 'free' retinoid concentrations, protecting retinoids from non-specific interactions, and chaperoning access of metabolic enzymes to retinoids. Implementation of the physiological effects of retinoids depends on the spatial-temporal expressions of binding proteins, receptors and metabolic enzymes. This review will discuss current understanding of the enzymes that catalyze retinol and retinoic acid metabolism and their unique and integral relationship to retinoid binding proteins.

Characteristics and responses of EBV immortalized B cells from periodontal disease patients

OBJECTIVE

This study was designed to examine human B cell responses to Actinobacillus actinomycetemcomitans (Aa). The general hypothesis to be tested was that Epstein-Barr virus (EBV) immortalized B cells could be used to investigate variations in B cell responsiveness of periodontitis patients to periodontal pathogens, and that B cells derived from the peripheral blood of periodontal disease patients infected with Aa demonstrate differences in in vitro activities compared to periodontally healthy subjects.

DESIGN

EBV-transformed B cell lines were used to analyze immunoglobulin and Aa-specific antibody responses, as well as to determine the frequencies of cells producing immunoglobulin (Ig) of a specific isotype and detect clones secreting antibodies specific for Aa. Lymphoblastoid cells lines (LCL) were derived by clonal transformation of peripheral blood lymphocytes from 10 Aa-infected patients with adult periodontitis (Aa-AP) and seven normal subjects.

METHODS

The B cells were incubated in Aa-coated polystyrene plates to separate adherent and non-adherent cells, and stimulate the cells with the whole bacteria. In addition, the B cells were stimulated with Aa LPS, E. coli LPS, or the polyclonal B cell activators (PBAs), pokeweed mitogen (PWM) and Staphylococcus aureus protein A (SpA). Both adherent and non-adherent cell populations were cultured for up to 15 days.

MAIN OUTCOME MEASURE

Total immunoglobulins (Igs) and antibody (IgG, IgA, IgM) levels to Aa in the culture supernatants were assessed using an ELISA. The distribution of IgG, IgA, IgM and Aa-specific antibody producing cells was analyzed by a double immunoenzymatic staining technique.

RESULTS

IgM levels produced by the LCLs were significantly increased vs IgG and IgA (P < 0.001). Three days after Aa stimulation, a marked increase in the level of total Igs and Aa-specific antibody was observed in adherent cells from Aa-AP (P < 0.05-0.03). Aa-specific antibody levels were significantly higher in the supernatants from Aa-AP vs normals throughout the culture interval (P < 0.03). There was also a significant increase in Aa-specific antibody levels after stimulation with Aa LPS or E. coli LPS (P < 0.05), whereas PWM and SpA had no significant effect on antibody to Aa. There was a predominance of IgM cells compared to IgG and IgA isotypes (P < 0.04) in LCLs from Aa-infected patients. After stimulation with Aa, a significant increase in the number of IgA (111%) and IgG (48%) secreting cells was observed, concomitant with a 74% decrease in the Ig-negative cell population. Total Aa+ cells increased significantly after stimulation (P < 0.001), predominated by Aa-specific IgG and IgM antibody producing cells.

CONCLUSIONS

These results showed that LCLs from Aa-infected patients were polyclonal with respect to isotype distribution. Further stimulation with Aa revealed a shift to cytoplasmic IgG and IgA expression, as well as increases in the Aa-specific B cell population. In contrast, the PBAs stimulated the LCLs to synthesize primarily IgM. Additionally, the findings indicated that: (1) without T cells, polyclonal activation of B cells may lead to elevated Aa-specific B cell populations; and (2) the presence of previously sensitized B cells is required to exert an antigen specific antibody response in the LCL. We conclude that secondary activation of primed B cells by oral bacteria or their products in advanced periodontal lesions may contribute to the local accumulation of significant numbers of Ig-producing cells. This report also suggested that EBV-mediated transformation can be used to probe B cell-bacterial interactions in studies of periodontitis.

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.

Effect of vitamin A supplementation on immunoglobulin G subclass responses to tetanus toxoid in children

Previously, we demonstrated that administering vitamin A supplements to children resulted in a significant increase in the immunoglobulin G (IgG) response generated against a vaccine dose of tetanus toxoid (TT) (R. D. Semba et al., J. Nutr. 122:101-107, 1991). However, from these analyses we could not determine whether there was an increase in levels of IgG of the subclass presumed to be important for protection against challenge by the toxin or whether there was simply a general increase in the levels of all the IgG subclasses expressing anti-TT activity. The goal of this study was to determine the profile of the anti-TT IgG subclasses in children receiving vitamin A supplementation or a placebo in order to assess the potential utility of the enhanced anti-TT response. In a randomized, double-masked, placebo-controlled clinical trial, the levels of the different anti-TT IgG subclasses were measured in 139 Indonesian preschool children (3 to 6 years of age) 2 weeks before and 3 weeks after immunization. Baseline anti-TT levels and immunization histories were used to separate those children who were responding to TT for the first time from those who responded in a secondary fashion because of previous exposure to TT. Children who were given vitamin A prior to immunization had significant increases in IgG1 levels regardless of whether they were undergoing primary or memory reactions. In the group of individuals who underwent a secondary response to TT, vitamin A supplementation was also associated with a modest but significant change in the levels of anti-TT IgG3. There were only minor changes in the levels of anti-TT IgG2 and IgG4. Since IgG1 is the subclass associated with a protective response to TT immunization, these results suggest that vitamin A supplementation may be a safe and effective intervention to enhance the relevant humoral response to TT and other vaccine antigens.