Expression of the cutaneous lymphocyte-associated antigen in circulating T cells in drug-allergic reactions

Background: Mechanisms underlying the production of delayed cutaneous reactions to drugs are poorly characterized. The cutaneous lymphocyte-associated antigen (CLA) is a skin-homing T cell receptor that defines T lymphocytes associated with the cutaneous immune response. We studied the percentage and activation phenotype of circulating CLA+ T cells in drug allergic patients and healthy controls. Methods: PBMCs were isolated from heparinized venous blood by Ficoll density gradient. Lymphocytes were stained for flow cytometry with anti-CLA, anti-CD3 and anti-HLA-DR mAbs. Five-parameter analysis was performed on an Ortho Cytoron Absolute flow cytometer. Results: We found increased percentages of circulating CLA+ T cells in drug-allergic patients compared to controls. Moreover, CLA+ T cells from drug-allergic individuals expressed a higher percentage of the T cell activation marker HLA-DR. Conclusions: These results suggest that CLA+ T cells may play a role in the pathology of delayed cutaneous reactions to drugs. Further studies are in progress to elucidate the role of skin-homing T cells in allergic reactions to drugs.