Skin Basement Membrane Zone: A Depository for Circulating Microbial Antigen Evoking Psoriasis and Autoimmunity

Background. Elevated levels of antibody to streptococcal exoenzymes have been found in patients with psoriasis or psoriatic arthritis. Research on the role of streptococcal antigen in psoriasis has been hampered by a potential molecular mimicry between streptococcal epitopes and human epidermal keratin. Objective and Methods. Evidence of microbial product was sought in skin biopsies of psoriasis patients thought clinically to have either strep-tococcal` skin. Staining was negative for nonpsoriatic subjects. Conclusions. The findings support a direct effect of microbial antigen in psoriasis. They also suggest an important role for SBMZ as a very large adhesive surface in the first step of a process of percutaneous epidermal elimination of foreign antigens and microbial toxins. The many autoimmune phenomena seen so often at the SBMZ are probably a physiologic part of this important immune function. Efforts to enhance the adhesive properties of SBMZ should be exploitable for both diagnostic and therapeutic benefit.