UCHL1+ (CD45RO+)‘memory’T cells predominate in the CD4+ cellular infiltrate associated with allergen-induced late-phase skin reactions in atopic subjects

Abstract

SUMMARY We have previously shown that CD4+ T lymphocytes accumulated at the site of allergen-induced late-phase reactions (LPR) in the skin of atopic subjects. In order to determine whether these were predominantly‘memory’or‘naive’cells, monoclonal antibodies recognizing isoforms of the CD45 common leucocyte antigen and immunocytochemical methods were used to study the composition of the T cell infiltrate. Allergen-induced late-phase skin reactions were biopsied6, 24 or 48 h after allergen challenge. Memory (CD45RO+/UCH L1+) T cells predominated and few naive (CD45RA/Leu 18+) cells were identified. Double immunofluorescence was used lo confirm that the UCHLI+ and Leu 18+ cells were CD4+ T lymphocytes. The selective recruitment of memory T cells to LPR sites is consistent with the active involvement of T lymphocytes in alopic allergic inflammation. A possible alternative explanation for apparently selective recruitment is the differential expression of endothelial adhesion molecules on memory and naive T lymphocytes.