Prenatal exposure to bisphenol A up-regulates immune responses, including T helper 1 and T helper 2 responses, in mice

Abstract

The effect of prenatal exposure to bisphenol A (BPA) on the immune system in mice was investigated. Virgin female mice were fed varying doses of BPA, on a daily basis, over a period of 18 days commencing on the day of pairing with stud males (day 0). On day 77, their male offspring of 8 weeks were immunized with hen egg lysozyme (HEL). Three weeks later, anti-HEL immunoglobulin G (IgG) in sera, and proliferative responses of spleen cells to the antigen, were measured. Anti-HEL IgG2a and interferon-gamma (IFN-gamma), secreted from splenic lymphocytes, were measured as indicators of T helper 1 (Th1) immune responses, while anti-HEL IgG1 and interleukin-4 (IL-4) were measured as indicators of Th2 responses. The results showed that fetal exposure to BPA was followed by significant increases in anti-HEL IgG as well as antigen-specific cell proliferation. Both Th1 responses (including anti-HEL IgG2a and IFN-gamma production) and Th2 responses (including anti-HEL IgG1 and IL-4 production) were augmented by prenatal exposure to BPA, although the augmentation of Th1 responses appeared to be greater than that of Th2 responses. Two-colour flow cytometric analysis showed that mice exposed prenatally to BPA had 29% and 100% more splenic CD3(+) CD4(+) and CD3(+) CD8(+) cells, respectively, than control animals. Similar results were obtained from females whose mothers had consumed BPA during pregnancy. These results suggest that prenatal exposure to BPA may result in the up-regulation of immune responses, especially Th1 responses, in adulthood.

Figure 1

Effect of fetal exposure to bisphenol A (BPA) on production of anti-hen egg lysozyme (HEL) immunoglobulin G (IgG). Female mice were administered per os (p.o.) the indicated doses of BPA, daily over a period of 18 days, commencing on the day of pairing with males (day 0). On day 77, male littermates of 8 weeks were immunized with HEL and, 3 weeks later, anti-HEL IgG in sera was measured as described in Materials and methods. Values represent the mean ± standard error of the mean (SEM) of five mice. ELISA, enzyme-linked immunosorbent assay. *P < 0·05 versus control (0 µg/kg BPA).

Figure 2

Effect of fetal exposure to bisphenol A (BPA) on proliferative responses of spleen cells to hen egg lysozyme (HEL). Female mice were administered per os (p.o.) the indicated doses of BPA, daily over a period of 18 days, commencing on the day of pairing with males (day 0). On day 77, male littermates of 8 weeks were immunized with HEL and, 3 weeks later, proliferative responses of spleen cells to HEL were measured as described in the Materials and methods. Values represent the mean ± standard error of the mean (SEM) of five mice. *P < 0·05 versus control (0 µg/kg BPA). c.p.m., counts per minute.

Figure 3

Effect of fetal exposure to bisphenol A (BPA) on the production of anti-hen egg lysozyme (HEL) immunoglobulin G 2a (IgG2a) and immunoglobulin G1 (IgG1). Female mice were administered per os (p.o.) the indicated doses of BPA, daily over a period of 18 days, commencing on the day of pairing with males (day 0). On day 77, male littermates of 8 weeks were immunized with HEL and, 3 weeks later, anti-HEL IgG2a and IgG1 in sera were measured as described in the Materials and methods. Values represent the mean ± standard error of the mean (SEM) of five mice. ELISA, enzyme-linked immunosorbent assay. *P < 0·05 versus control (0 µg/kg BPA).

Figure 4

Effect of fetal exposure to bisphenol A (BPA) on the secretion of T helper 1 (Th1) and T helper 2 (Th2) cytokines. Female mice were administered per os (p.o.) the indicated doses of BPA, daily over a period of 18 days, commencing on the day of pairing with males (day 0). On day 77, male littermates of 8 weeks were immunized with HEL and, 3 weeks later, secretion of interferon-γ (IFN-γ) and interleukin-4 (IL-4) by spleen cells was measured as described in the Materials and methods. Values represent the mean ± standard error of the mean (SEM) of five mice. *P < 0·05 versus control (0 µg/kg BPA).

Figure 5

Two-colour flow cytometric analysis of the expression of CD3, CD4 and CD8 on splenic lymphocytes from mice exposed to bisphenol A (BPA) during fetal life. Female mice were administered per os (p.o.) the indicated doses of BPA, daily over a period of 18 days, commencing on the day of pairing with males (day 0). On day 77, splenic lymphocytes from male (a, b, e, f) or female (c, d, g, h) littermates of 8 weeks exposed to control (a, c, e, g) and BPA (b, d, f, h) were stained with anti-mouse CD4, CD8, and CD3 monoclonal antibodies, as described in the Materials and methods.