Induction of the Aryl Hydrocarbon Receptor–Responsive Genes and Modulation of the Immunoglobulin M Response by 2,3,7,8-Tetrachlorodibenzo-p-Dioxin in Primary Human B Cells

Abstract

Past studies in rodent models identified the suppression of primary humoral immune responses as one of the most sensitive sequela associated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure. Yet, the sensitivity of humoral immunity to TCDD in humans represents an important toxicological data gap. Therefore, the objectives of this investigation were two-fold. The first was to assess the induction of known aryl hydrocarbon receptor (AHR)-responsive genes in primary human B cells as a measure of early biological responses to TCDD. The second was to evaluate the direct effect of TCDD on CD40 ligand-induced immunoglobulin M (IgM) secretion by human primary B cells. The effects of TCDD on induction of AHR-responsive genes and suppression of the IgM response were also compared with B cells from a TCDD-responsive mouse strain, C57BL/6. AHR-responsive genes in human B cells exhibited slower kinetics and reduced magnitude of induction by TCDD when compared with mouse B cells. Evaluation of B-cell function from 12 donors identified two general phenotypes; the majority of donors exhibited similar sensitivity to suppression by TCDD of the IgM response as mouse B cells, which was not attributable to decreased B-cell proliferation. In a minority of donors, no suppression of the IgM response by TCDD was observed. Although donor-to-donor variation in sensitivity to TCDD was observed, human B cells from the majority of donors evaluated showed impairment of effector function by TCDD. Collectively, data presented in this series of studies demonstrate that TCDD impairs the humoral immunity of humans by directly targeting B cells.

The Influence of Human Interindividual Variability on the Low-Dose Region of Dose-Response Curve Induced by 2,3,7,8-Tetrachlorodibenzo-p-Dioxin in Primary B Cells

“…Approximately 11% (6 of 51) of the donors appeared nonresponsive to TCDD-induced decrease in the number of B cells secreting IgM. This is similar to previously published research (Lu et al, 2010). In contrast to "responsive" donors whose B cells displayed significant suppression at !…”

“…The number of IgM-secreting cells was quantified by enzymelinked immunospot (ELISPOT) as previously described (Lu et al, 2010). Briefly, multiscreen 96-well filter plates (Millipore, Billerica, Massachusetts) were coated with antihuman IgM antibody (5 lg/ml) (Sigma Aldrich, St. Louis, Missouri) overnight and, subsequently, blocked with 5% bovine serum albumin (Sigma).…”

“…Within the immune system, TCDD has been established to directly alter B-cell function as evidenced by the suppression of humoral immune responses (Crawford et al, 2003;Sulentic et al, 1998). Although much of the current understanding of TCDD-induced B-cell dysfunction has been derived from mouse studies and murine cell lines, recent publications using primary cells have confirmed that TCDD suppresses the activation and differentiation of human B cells (Lu et al, 2010(Lu et al, , 2011Phadnis-Moghe et al, 2015). Furthermore, results from studies using a primary B-cell model indicated that a subset of the human donors did not respond to TCDD suggesting that this model might be valuable in modeling interindividual variability (Lu et al, 2010).…”

“…Two TCDD-sensitive endpoints were analyzed: (1) the number of IgM-secreting cells and (2) the quantity of IgM secreted during the period of culture (Crawford et al, 2003;Lu et al, 2010). The results from the endpoints were statistically modeled at the individual level and as an averaged population to address the potential effect of increasing interindividual variability in the shape of a DRR.…”

Effects of AhR ligands on the production of immunoglobulins in purified mouse B cells

“…In addition, our data indicated that ITE inhibited B cell differentiation into Ig-producing plasma cells. In previous papers, the highly potent AhR agonist TCDD was shown to suppress the production of IgM in human B cells and a lipopolysaccharide (LPS)-induced transformed mouse B cell line, CH12.LX, and to inhibit the differentiation into Igproducing plasma cells (11,12,20,21). More recently, it was reported that benzo[a]pyrene also suppressed the differentiation into plasma cells in human B cells (2).…”