Specific IgA and CLA+ T-cell IL-17 response to Streptococcus pyogenes in psoriasis.

Streptococcus pyogenes tonsillar infection is well-known to trigger and exacerbate psoriasis lesions in both guttate and plaque forms of the disease. Although mucosal and cutaneous tissues are closely involved in psoriasis pathology, the interaction between their specific immune responses has not been deeply explored. This work aims to address and characterize the presence of humoral responses against Streptococcus pyogenes in psoriasis patients and its putative association with cytokine responses detected in vitro in our psoriasis ex vivo model, based on the coculture of CLA+/- T cells with autologous epidermal cells. Psoriasis patients presented increased IgA response to S. pyogenes when compared to control subjects. Surprisingly, in plaque psoriasis patients, despite being negative for anti-streptolysin O antibody titer, IgA plasma levels against S. pyogenes correlated with CLA+ T cell dependent IL-17F response in vitro. Not association is observed for IgG levels in plaque psoriasis. Similar association is observed for IgA anti-SE and IL-17A in guttate psoriasis patients. We propose S. pyogenes specific IgA as a potential new perspective for better understanding the role of S. pyogenes in psoriasis development.