Antigen-primed splenic CD8(+) T cells impede the development of oral antigen-induced allergic diarrhea

Background: Although CD4(+) T-cell populations are thought to be involved in the pathophysioiogy of food allergy and oral tolerance, the role of CD8(+) T cells remains uncertain. Objective: We analyzed regulatory effects of adoptively transferred CD8(+) T cells on the development of allergic diarrhea in antigen-sensitized mice that had a significantly reduced number of conventional TCR alpha beta(+) CD8(+) T cells. Methods: Ovalbumin-specific T-cell receptor transgenic mice were systemically sensitized to ovalbumin. Splenic CD8(+) T cells purified from ovalbumin-sensitized or nonsensitized wild-type mice or IL-10 knockout mice were adoptively transferred to ovalbumin-sensitized ovalbumin-specific T-cell receptor transgenic mice. Allergic diarrhea induced by oral administration of ovalbumin, ovalbumin-specific immunoglobulin production, and cytokine production in intestines and mesenteric lymph nodes were assessed. Results: Adoptive transfer of splenic CD8(+) T cells from ovalbumin-primed mice, but not from nonprimed mice, suppressed the development of allergic diarrhea, which was associated with in vivo increased IL-10 mRNA expression and in vitro antigen-specific IL-10 production by mesenteric lymph node cells. Upregulation of serum ovalbumin-specific IgE was not suppressed by ovalbumin-primed CD8(+) T-cell transfer. Although administration of IL-10 before ovalbumin challenge failed to alleviate allergic diarrhea, transfer of splenic CD8(+) T cells from IL-10 knockout mice showed diminished preventive effects. Conclusion: Systemic immunization with allergen simultaneously induces regulatory CD8(+) T cells that can inhibit the development of allergic diarrhea. IL-10 production by regulatory CD8(+) T cells appears to be partially involved in these inhibitory mechanisms. (J Allergy Clin Immunol 2009;123:889-94.)