T-cell receptor repertoire in pyoderma gangrenosum: evidence for clonal expansions and trafficking

Background The cause of pyoderma gangrenosum (PG) is unknown, but it is likely to be an immune-mediated disease because it is often associated with conditions such as inflammatory bowel disease and rheumatoid arthritis. T cells play an important role in these conditions and have been implicated in the pathogenesis of other skin diseases such as psoriasis. Objectives We examined the T-cell receptor repertoire in PG in order to test the hypothesis that if the T cells were responding to antigen, there would be expanded T-cell clones in the skin and the circulation of these patients. Patients and methods We studied five patients with PG and examined the T-cell receptor repertoire in cells taken from the peripheral blood and from biopsies of the ulcers, using complementarity determining region 3 spectratyping. Results We were able to demonstrate expanded clones in the peripheral blood lymphocyte population of each patient. Clonal expansions within the skin were found in four of the five patients. Most significantly, expanded clones that were shared between the blood and the skin were revealed in four of the five patients. Conclusions These findings imply that T cells play an integral role in the development of PG and suggest that T cells are trafficking to the skin under the influence of an antigenic stimulus.