Abstract: Objective To investigate the role of skin homing T lymphocytes in the development of psoriasis vulgaris(PV). Methods Indirect immunofluorescent double staining technique was employed to study the expression of infiltrating skin homing T lymphocytes in normal, uninvolved perilesional and lesional psoriatic skin in different stages (progressing, stable or regressing) and in normal human skin. Results ①Expression of cutaneous lymphocyte associated antigen (CLA) was found in the majority of CD3⁺T lymphocytes in normal human skin and in lesions of PV, and CD45RO phenotype was expressed in almost all CLA⁺T lymphocytes. ②In psoriatic lesions, the number of CD4⁺CLA⁺ and CD8⁺CLA⁺ cells was higher in progressive stage than that in stable stage(P<0.05); the number of CD4⁺CLA⁺ cells was higher in stable stage than that in regressive stage(P<0.05). The number of CD8⁺CLA⁺ cells was higher in regressive stage of psoriatic lesions than that in normal appearing skin of psoriasis(P<0.05). The number of CD4⁺CLA⁺ and CD8⁺CLA⁺ cells of uninvolved perilesional psoriatic appearing skin was higher in progressive stage than that in stable stage(P<0.05). ③A great number of CLA⁺ dendritic cells was found in the lesional epidermis of some psoriatic patients, but not found in normal human skin. Conclusions In both normal human skin and psoriatic skin, the majority of T lymphocytes are skin homing (CLA⁺) T lymphocytes. Intraepidermal and dermal infiltrating T cells in lesions of PV belong predominantly to CD3⁺, CD4⁺, CD45RO⁺, CLA⁺ subsets, and these cells may play an important role in the pathogenesis of PV.

Key words: Psoriasis, Lymphocyte function associated antigen, Receptors,lymphocyte homing