The present invention relates to the use of Yersinia outer protein M (YopM)in the prevention and/or treatment of psoriasis by cutaneous, intradermalor subcutaneous administration. In particular,the present invention relates to the use of YopM in the treatment of plaque psoriasis, guttate psoriasis, inverse psoriasis, pustular psoriasis, erythrodermic psoriasis, arthritis psoriasis.