γδ T cells assist αβ T cells in the adoptive transfer of contact hypersensitivity to para-phenylenediamine

Abstract

Summary Para-phenylenediamine (PPD) is known to be a common sensitizer of allergic contact dermatitis and contact urticaria. To clarify the mechanism of contact hypersensitivity (CHS) to PPD, we established a mouse model of PPD-induced CHS. BALB/c mice were immunized for 3 consecutive days by painting topically a 2·5% PPD solution on their shaved abdominal skin. On days 5, 7 or 9 after the initial application, the mice were challenged by applications of a 2·5% PPD solution. Maximal ear swelling was determined at 24 h but another statistically significant and smaller ear swelling was observed 1 h after challenge with PPD in a hapten-specific manner. Adoptive cell transfer experiments demonstrated that the ear swelling of the adoptive cell transferred mice displayed an early response at 6 h and a late response from 12 h to 24 h when the recipient mice were challenged immediately after transfer. Both MoAbs and complement treatment of the transferred cells demonstrated that the phenotype of the early response cells which elicited a response at 6 h after challenge was Thy1+, B220+, αβ TCR, γδ TCR, CD3, CD4, CD5+ and CD8. The in vitro treatment of effector cells with MoAbs against not only αβ TCR but also γδ TCR, together with complement, was found to diminish substantially the late response, elicited 12–24 h after challenge. γδ T cells reconstituted the ability of αβ T cells to transfer 24 h CHS responsiveness. The phenotype of the γδ T cells that assist CHS effector αβ T cells was CD3+, CD4 and CD8+ and these regulatory γδ T cells were neither Ag-specific nor MHC-restricted. Furthermore, γδ T cells from normal spleen could also assist αβ T cells in adoptive transfer of the 24 h CHS response in a non-MHC-restricted manner. RT-PCR demonstrated that αβ T cells strongly expressed mRNA IFN-γ, whereas γδ T cells expressed not only IFN-γ but also IL-4 and IL-10. These data indicate that not only early response cells and αβ T cells but also Th2 type γδ T cells may play an important role in the elicitation of CHS to PPD.