1alpha,25-dihydroxyvitamin D3 inhibits anti-CD40 plus IL-4-mediated IgE production in vitro.

In the present study, we examined whether anti-CD40+IL-4-mediated B cell proliferation and immunoglobulin synthesis is affected by vitamin D (VD) and its low-hypercalcemic analogue EB1089 in Bcells from healthy donors. Analysis of vitamin D receptor (VDR) expression showed that only anti-CD40+IL-4-stimulated, but not resting B cells express VDR. Studies on B cell proliferation revealed that anti-CD40+IL-4-mediated proliferation of B cells was not affected by VD or EB1089. By contrast, IgE synthesis was markedly inhibited by both, VD and EB1089, starting at concentrations from 10(-10) M for VD and 10(-12) M for EB1089, with maximal inhibition at 10(-6) M (VD 85.5+/-9.7%; EB1089 77.3+/-10.8%). The production of the other Ig (IgA and IgG) was not significantly inhibited by VD after anti-CD40+IL-4 stimulation, and IgM production was only slightly reduced (18.7+/-7.9%). These observations were confirmed by intracellular staining of the different isotypes in B cells after anti-CD40+IL-4 stimulation, which showed a strong reduction of IgE(+) cells in the presence of VD. Analyses of molecules that are known to affect IgE production (CD23 and IL-6) revealed that these are not involved in VD-dependent inhibition of IgE production. By contrast, epsilon germ-line transcription was inhibited by VD (41.2+/-26.1%; n=5), as was NF-kappaB (p50 and p65) protein expression in stimulated cells. These data show that VD and its analogue EB1089 inhibit IgE production of anti-CD40+IL-4-stimulated B cells in vitro. The involved mechanism includes epsilon germ-line transcription, NF-kappaB activation and switch recombination suggesting that complex mechanisms of VD action in anti-CD40+IL-4-stimulated B cells are responsible.

Inhibition of IgE production by the imidazoquinoline resiquimod in nonallergic and allergic donors.

The aim of this study was to examine whether the immune modulator resiquimod, which belongs like imiquimod to the imidazoquinolines, is capable of influencing IgE synthesis. Peripheral blood mono-nuclear cells from normal donors and patients with atopic dermatitis and with seasonal allergic rhinitis were analyzed in the presence of resiquimod, anti-CD40+interleukin-4 stimulation for induction of IgE, and anti-CD40+interleukin-4 in the presence of resiquimod, respectively. Our data show that spontaneous IgE production was inhibited in the presence of resiquimod, which was strongest at 10 ng per ml in both groups of allergic patients. Inhibition of IgE production after anti-CD40+interleukin-4 stimulation in the presence of resiquimod (10 ng per ml) was comparable between all the groups. In normal donors median inhibition of IgE synthesis was 93%, in seasonal allergic rhinitis patients 77%, and in patients with atopic dermatitis 72%. In order to rule out antiproliferative effects of resiquimod, which might influence IgE production, we also studied proliferation of peripheral blood mononuclear cells from normal donors, which remained unchanged in the presence of resiquimod at 0.1-10 ng per ml but was inhibited at 100 or 1000 ng per ml. In search of possible mechanisms responsible for the observed inhibition of IgE production, we analyzed the expression and production of molecules that are known to modulate IgE production, namely CD23 and interferon-gamma. CD23 expression on B cells was lower in the presence of resiquimod (10 ng per ml) in anti-CD40+interleukin-4 stimulated cells, whereas interferon-gamma was strongly induced (4-6-fold) by resiquimod (10 ng per ml). Furthermore, by using neutralizing interferon-gamma monoclonal antibodies, we show that inhibition of IgE production occurred in an interferon-gamma-dependent manner. Taken together our results show that resiquimod is a potent modulator of IgE production in vitro in normal but also in allergic donors.