tretinoin and Common-Variable-Immunodeficiency

In the present study, we aimed at identifying the mechanisms whereby the vitamin A metabolite all-trans retinoic acid (RA) promotes the formation of plasma cells upon stimulation of B cells via the innate immunity receptors TLR9 and RP105. Most often, differentiation of B cells involves the sequential events of class switch recombination and somatic hypermutations characteristic of germinal center reactions, followed by plasma cell formation. By studying the regulatory networks known to drive these reactions, we revealed that RA enhances the expression of the plasma cell-generating transcription factors IFN regulatory factor (IRF)4 and Blimp1, and paradoxically also activation-induced deaminase (AID) involved in somatic hypermutations/class switch recombination, in primary human B cells. IRF4 was identified as a particularly important protein involved in the RA-mediated production of IgG in TLR9/RP105-stimulated B cells. Based on kinetic studies, we present a model suggesting that the initial induction of IRF4 by RA favors AID expression. According to this model, the higher level of IRF4 that eventually arises results in sustained elevated levels of Blimp1. Regarded as a master regulator of plasma cell development, Blimp1 will in turn suppress AID expression and drive the formation of IgG-secreting plasma cells. Notably, we demonstrated IRF4 to be deregulated in B cells from common variable immunodeficiency patients, contributing to the observed aberrant expression of AID in these patients. Taken together, the present study both provides new insight into the mechanisms whereby RA induces differentiation of B cells and identifies IRF4 as a key to understand the defective functions of B cells in common variable immunodeficiency patients.

Topics: Adult; Aged; Antigens, CD; B-Lymphocytes; Base Sequence; Cell Differentiation; Common Variable Immunodeficiency; Cytidine Deaminase; Female; Gene Expression Regulation; Germinal Center; Humans; Immunoglobulin Class Switching; Immunoglobulin G; Interferon Regulatory Factors; Lymphocyte Activation; Male; Middle Aged; Molecular Sequence Data; Plasma Cells; Positive Regulatory Domain I-Binding Factor 1; Repressor Proteins; RNA Interference; RNA, Small Interfering; Somatic Hypermutation, Immunoglobulin; Toll-Like Receptor 9; Tretinoin

Common variable immunodeficiency (CVID) is a disease that is characterized primarily by low levels of serum Igs, resulting in a high incidence of infections. It also has been associated with impaired B cell signaling via TLR9 and reduced serum levels of vitamin A. Given the established link between vitamin A deficiency and increased susceptibility to infections, we investigated the ability of the vitamin A metabolite all-trans retinoic acid (RA) to restore the defective immune responses in CVID-derived B cells activated through the TLRs TLR9 and RP105. We demonstrate that RA almost normalizes proliferation and IL-10 secretion in patient-derived B cells. IgG secretion is also partially restored, but to a more moderate extent. This can be explained by impaired RA-mediated isotype switching in TLR9/RP105-stimulated CVID-derived B cells owing to reduced induction of activation-induced deaminase. Accordingly, these B cells secreted higher levels of IgM than did normal B cells, and RA augmented IgM secretion. The ability of RA to improve critical immune parameters in CVID-derived B cells stimulated through TLR9 and RP105 support the possibility of combining RA with TLR stimulation for the treatment of CVID.

Topics: ADP-ribosyl Cyclase 1; Adult; Aged; Antibody Formation; Antigens, CD; B-Lymphocytes; Case-Control Studies; Cell Differentiation; Cell Proliferation; Common Variable Immunodeficiency; Female; Humans; Immunoglobulin G; Interleukin-10; Lymphocyte Activation; Male; Middle Aged; Plasma Cells; Positive Regulatory Domain I-Binding Factor 1; Receptors, Retinoic Acid; Repressor Proteins; Toll-Like Receptor 9; Tretinoin; Young Adult

The underlying nature of the defect of CVID is not understood, and the treatment at present is life-long infusion of replacement immunoglobulin. Attempts have been made to use other therapeutic agents, such as IL-2 and retinoic acid (RA), with mixed results. RA is a morphogenetic signalling molecule related to vitamin A and involved in vertebrate development. We report here our in vitro evaluation of the effects of three vitamin A analogues, 9-cis retinal, 13-cis RA and all-trans RA, on antibody production of PBMC from normal donors and patients with CVID. At 10(-5) M, 9-cis retinal strongly augmented IgM production of lymphocytes from normal individuals and to a much lesser extent, mild, non-granulomatous (group C) CVID patients, but IgG production was not affected. In the presence of anti-human IgM and IL-2, 9-cis retinal at 10(-5) M elevated IgM and IgG production by normal PBMC, but the effect on PBMC of mild CVID was minimal. The effect of 9-cis retinal was significantly reduced at 10(-7) and 10(-9) M. Only minimal effects were found using 13-cis RA and all-trans RA under these conditions. No detectable antibody production was found in severe, granulomatous (group A) CVID patients under any conditions tested. Taking all data into account, 9-cis retinal is the most potent stimulator for antibody production compared with 13-cis RA and all-trans RA as tested in this in vitro study.

Topics: Blood Donors; Cells, Cultured; Common Variable Immunodeficiency; Diterpenes; Humans; Immunoglobulins; Isotretinoin; Leukocytes, Mononuclear; Retinaldehyde; Tretinoin; Vitamin A

Human-human B cell hybridoma JK32.1, constructed from B lymphocytes of a common variable immunodeficient patient and nonsecreting cell line, retains the defects of B cell immunodeficiency. Efforts to clarify whether the defect is located within the plasma membranes of this cell line were carried out by implanting them with plasma membrane fraction derived from normal functional cells via intact non-infectious Sendai virus. The implanted cells were activated with various mitogens and their Ig responses and isotype switching were examined. Restoration of IgM secretion was achieved in the implanted JK32.1 cells following stimulation with SAC, PWM, or retinoic acid. Augmented IgM response was also obtained in the implanted cells treated with retinoic acid and lipopolysaccharide (LPS) despite their unresponsiveness to LPS alone. No IgG or IgA response could be detected in the implanted JK32.1 cells. These data suggest that this immunodeficient cell line possesses at least two different malfunctions, one located within the plasma membrane moiety of the cells and the other located within the cytoplasmic and/or nucleic components. The plasma membrane moiety defect can be repaired temporarily by delivering proper signals via the implanted plasma membranes. However, this manipulation of the cells could not overcome the intrinsic defect of the cells which blocks isotype switching and secretion of IgG, IgE, and IgA antibodies.

Topics: Animals; B-Lymphocytes; Cell Line; Cell Membrane; Common Variable Immunodeficiency; Female; Humans; Immunoglobulin M; Lipopolysaccharides; Membrane Fusion; Mice; Mice, Inbred BALB C; Mitogens; Phytohemagglutinins; Pokeweed Mitogens; Staphylococcus aureus; Tretinoin