Role of staphylococcal enterotoxins in pathogenesis of atopic dermatitis: growth and expression of T cell receptor Vβ of peripheral blood mononuclear cells stimulated by enterotoxins A and B

Abstract

In order to investigate the role of staphylococcal enterotoxins in the pathogenesis of dermatitis in atopic patients, the growth and expression of T cell receptor Vβ in peripheral blood mononuclear cells (PBMCs) from atopic dermatitis patients induced by stimulation with staphylococcal enterotoxin A (SEA) or staphylococcal enterotoxin B (SEB) were examined. Lymphocyte stimulation tests (LST) using SEA or SEB were performed in atopic dermatitis (AD) patients ( n = 10) and normal controls ( n = 5). PBMCs from AD patients displayed significantly stronger responses to SEA or SEB than those from the controls. To ascertain further whether SEA acts as a superantigen in atopic dermatitis, the expression of 22 genes in the variable region of the β chain (Vβ) of T cell receptors (TcR) was examined before and after stimulation with SEA by a reverse transcriptase-polymerase chain reaction (RT-PCR). Before stimulation, only weak expression of Vβ was observed, and the expression of the various Vβ segments was uniform in the normal controls ( n = 3). In the AD patients ( n = 3), the expression of Vβ was enhanced, but was not uniform in 2 out of 3 patients and the pattern of expression was characteristic in each individual. This suggests that Vβ expression varies in individual AD patients and displays restricted heterogeneity, reflecting the diversity of the etiology of the disease. After culture of the SEA-stimulated cells, no difference was observed in the expression of TcR Vβ segments in the 3 normal controls as compared with that prior to stimulation, but particular Vβ segments were intensely expressed in 3 AD patients, displaying distinct patterns (case 1: Vβ9, Vβ10, Vβ18; case 2: Vβ6.1-3; case 3: Vβ6.1-3, Vβ18). Many of these Vβ segments corresponded with those known to be induced by SEA. These results suggest oligoclonal proliferation of T cells in the peripheral blood of AD patients and high responsiveness in each clone, and since the expression of Vβ segment after SEA stimulation was restricted, the actions of staphylococcal enterotoxins as superantigens were suggested.