The expression of γΔ T cell receptor and the prevalence of primed, activated and IgA-bound T cells in Behçet's syndrome

Abstract

SUMMARY Mucosal ulceration of the oral, and to a lesser extent genital tissues is an essential feature of Behçet's syndrome and is associated with changes in the IgA class of immune responses. Indeed, a significant increase in the proportion of cytophilic IgAl was found in circulating CD8 and CD4 cells (P < 0.01), with a corresponding decrease in IgA-Fc receptors on these T cells. Furthermore, 30–40% of the cytophilic IgA1 on T cells may have been of the polymeric secretory type and the rest of the monomeric variety. IgA isotype of B cells was also significantly increased (P < 0.001), without an overall change in circulating B cells. However, a surprising finding was the significant up-regulation of γŞ T cell receptor in the CD8 (P < 0.01) in the absence of a change in the proportion of αβ T cell receptor. The results suggest that some common microbial antigen might initiate at the mucosal surface an immune defence reaction characterized by T cells with γΔ receptors and IgA-specific B cells. However, IgAl bound to circulating T cells may down-regulate the central T cell function.