Contrasting patterns of streptococcal superantigen-induced T-cell proliferation in guttate vs. chronic plaque psoriasis

Background: Streptococcal infection is strongly associated with guttate psoriasis (GP) and may also exacerbate chronic plaque psoriasis (CPP), possibly through the release of superantigenic toxins. Objectives: To investigate superantigen-induced generation of cutaneous lymphocyte associated antigen (CLA) -positive lymphocytes in GP compared with CPP. Methods: Peripheral blood lymphocyte (PBL) expression of CLA and T-cell receptor Vβ chain was assessed in patients with CPP and with active and resolved GP. Expression of superantigen-reactive Vβ families was compared with in vitro superantigen-induced peripheral blood mononuclear cell (PBMC) proliferation. Results: Peripheral blood mononuclear cells from patients with active GP showed a twofold increased proliferation after stimulation with streptococcal pyogenic toxins A and streptococcal pyogenic toxins C compared with controls (P<0.01), whereas the response to the staphylococcal toxins and mitogenic stimulation was the same in all groups. Peripheral blood lymphocytes (PBL) from patients with active GP showed increased use of the superantigen-reactive families Vβ2 (P<0.01) and Vβ17 (P<0.05), which was not evident in the other patient groups or controls. This pattern of Vβ expression was only observed in CLA-positive T cells. Furthermore, there was a positive correlation between Vβ2 expression and enhanced proliferation after stimulation with SPEA (r=0.82, P<0.01) and SPEC (r=0.74, P<0.05) in active GP. Conclusions: This study supports the concept that streptococcal infection precipitates acute GP at least in part through superantigen driven generation of Vβ-restricted CLA-positive skin homing lymphocytes, whereas we could find no evidence for a similar mechanism occurring in the maintenance of stable CPP.