The influence of IgE-enhancing and IgE-suppressive gammadelta T cells changes with exposure to inhaled ovalbumin

Abstract

It has been reported that the IgE response to allergens is influenced by gammadelta T cells. Intrigued by a study showing that airway challenge of mice with OVA induces in the spleen the development of gammadelta T cells that suppress the primary IgE response to i.p.-injected OVA-alum, we investigated the gammadelta T cells involved. We found that the induced IgE suppressors are contained within the Vgamma4(+) subset of gammadelta T cells of the spleen, that they express Vdelta5 and CD8, and that they depend on IFN-gamma for their function. However, we also found that normal nonchallenged mice harbor IgE-enhancing gammadelta T cells, which are contained within the larger Vgamma1(+) subset of the spleen. In cell transfer experiments, airway challenge of the donors was required to induce the IgE suppressors among the Vgamma4(+) cells. Moreover, this challenge simultaneously turned off the IgE enhancers among the Vgamma1(+) cells. Thus, airway allergen challenge differentially affects two distinct subsets of gammadelta T cells with nonoverlapping functional potentials, and the outcome is IgE suppression.

Figure 1

Altered IgE response in γδ T cell-modified mice. (a) Background serum IgE levels and primary OVA/alum-induced IgE responses in genetically altered mouse strains. Total serum IgE concentrations in C57BL/6, B6.TCR-β^−/−, B6.TCR-β^−/−/δ^−/−, B6.TCR-δ^−/−, B6.TCR-Vγ4^−/−/6^−/−, and B6.TCR-Vγ1 Tg mice was measured using sandwich ELISA 14 days after i.p. injection of OVA/alum, and in non-treated controls. Results for each group are expressed as the mean +/− SEM (n=18, 4, 4, 20, 15, 6, in the order shown). NT, Non-treated; ***, Significant difference (p < 0.001) compared to OVA-challenged C57BL/6 mice. Note: Significant differences in basal IgE levels between the mouse strains shown in Fig. 1a are listed in the text. (b) Effect of treatment with anti TCR-mAbs on the primary OVA/alum-induced IgE response in C57BL/6 mice. Normal C57BL/6 mice were injected i.v. with non-specific hamster IgG (HIgG), anti-TCR-δ, anti-TCR-Vγ4, and anti-TCR-Vγ1 mAbs on day -4, and total serum IgE concentrations were determined on day 14 after i.p. injection of OVA/alum. Mice that received the OVA/alum injection but no antibody treatment were included as controls. Results for each group are expressed as the mean +/− SEM (n=4 in each group). *, Significant difference compared to untreated or HIgG-treated controls (p < 0.05).

Figure 2

Primary OVA/alum-induced IgE-response in B6.TCR-δ^−/− mice is inhibited following adoptive transfer of Vγ4⁺ cells from airway-OVA-challenged B6.TCR-β^−/−mice. Purified Vγ4⁺ cells (3×10⁴/inoculum) from naïve or 10N-treated B6.TCR-β^−/− mice, or from 10N-treated B6.TCR-β^−/−/IFN-γ^−/− - mice were adoptively transferred i.v. to B6.TCR-δ^−/− recipients, just prior to i.p. OVA/alum injection. Serum total IgE (a) and OVA-specific IgE (b) levels were measured 14 days after the OVA/alum treatment.Results for each group are expressed as the mean +/− SEM (n=4 in each group). Significant differences between mice that received cells and those that received no cells are indicated. **, p < 0.01; ***, p < 0.001. NS, not significant.

Figure 3

IgE-suppressive Vγ4⁺ γδ T cells co-express Vδ5. Vδ5⁺ and Vδ5⁻ Vγ4 cells were purified from the spleen of 10N-treated B6.TCR-β^−/− mice by FACS-sorting. Purified Vγ4⁺/Vδ5⁺ or Vγ4⁺/Vδ5⁻ cells (3×10⁴/inoculum) were adoptively transferred i.v. to B6.TCR-δ^−/− recipients just prior to i.p. injection of OVA/alum. Serum total IgE (a) and OVA-specific IgE (b) levels were measured 14 days after the OVA/alum injection. Results for each group are expressed as the mean +/− SEM (n=4 in each group). Significant differences between mice that received cells and those that received no cells are indicated. ***, p < 0.001. NS, not significant.

Figure 4

IgE-suppressive Vγ4⁺ γδ T cells express CD8. CD8α⁺ and CD8α⁻ Vγ4 cells were purified from the spleen of 10N-treated B6.TCR-β^−/− mice by FACS-sorting. 3×10⁴ cells of each type were adoptively transferred i.v. to B6.TCR-δ^−/− recipients just prior to i.p. injection of OVA/alum. Serum total IgE levels were measured 14 days after the OVA/alum injection. Results for each group are expressed as the mean +/− SEM (n=4 in each group). Significant differences between mice that received cells and those that received no cells are indicated. ***, p < 0.001. NS, not significant.

Figure 5

Adoptively transferred Vγ1⁺ γδ T cells from non-treated but not airway-OVA-challenged B6.TCR-β^−/− mice enhance the primary OVA/alum-induced IgE response in B6.TCR-δ^−/− mice. Purified Vγ1⁺ cells (3×10⁴/inoculum) from non-treated or 10N-treated B6.TCR-β^−/− mice were adoptively transferred i.v. to B6.TCR-δ^−/− recipients just prior to i.p. OVA/alum injection. Serum total IgE (a) and OVA-specific IgE (b) levels were measured 14 days after the OVA/alum injection. Results for each group are expressed as the mean +/− SEM (n=4 in each group). Significant differences between mice that received cells and those that received no cells are indicated. *, p < 0.05; **, p < 0.01. NS, not significant.

Figure 6

Co-expression of Vδ5 is not required for Vγ1⁺ γδ T cells from non-treated mice to enhance the primary OVA/alum-induced IgE response. Purified Vγ1⁺/Vδ5⁺ or Vγ1⁺/Vδ5⁻ cells (3×10⁴/inoculum) from non-treated B6.TCR-β^−/− mice were adoptively transferred i.v. to B6.TCR-δ^−/− recipients directly before antigen challenge. Serum total IgE (a) and OVA-specific IgE (b) levels were measured 14 days after the OVA/alum injection. Results for each group are expressed as the mean +/− SEM (n=4 in each group). Significant differences between mice that received cells and those that received no cells are indicated. *, p < 0.05; **, p < 0.01.

Figure 7

Net-effect of total γδ T cells on the primary OVA/alum-induced IgE response. Purified γδ T cells (3×10⁴/inoculum) from non-treated or OVA-challenged (10N) B6.TCR-β^−/− mice were adoptively transferred i.v. to B6.TCR-δ^−/− recipients directly before antigen challenge. Serum total IgE (a) and OVA-specific IgE (b) levels were measured 14 days after the OVA/alum injection. Results for each group are expressed as the mean +/− SEM (n=4 in each group). Significant differences between mice that received cells and those that received no cells are indicated. *, p < 0.05; **, p < 0.01, ***, p < 0.001.