Distribution of T lymphocyte Subpopulations in Psoriatic Skin

Sung, Kyung Jeh; Kim, Hyun Soo; Suh, Jung Wha; Choi, Jee Ho

Abstract

BACKGROUND: Although the main features of psoriasis consist of abnormal epidermal proliferation and T cell infiltration, which of these is the initial abnormality has been a longstanding unresolved question. Recently there has been definite evidence that activated T cells produce the cytokines that induce keratinocyte abnormalities.
OBJECTIVE
We investigated the distributions and relative numbers of T lymphocyte subpopulations, that is, CD4+ and CD8+ T cells, to verify the more important T cell subtype and its infiltrating site in the formation of psoriatic lesions.
METHODS
Paired psoriatic lesional and non-lesional skin tissues were obtained from eight typical psoriatic patients. Immunohistochemical staining was done on the frozen sections using a labelled streptavidin-biotin peroxidase complex method with DAKO LSAB kit. The primary antibodies used in this study were monoclonal or polyclonal antibodies against CD3, CD4, CD8, HLA-DR, and ICAM-1.
RESULTS
In lesional psoriatic skin, the epidermis was mainly infiltrated by CD8+ T cells. There were little or no T cells in non-lesional epidermis. In both lesional and non-lesional dermis, CD4+ T cells were the main ones. In lesional skin, anti-ICAM-1 antibody positively stained diffusely in the endothelial cells of papillary and subpapillary plexuses and focally in epidermal keratinocytes, but in non-lesional skin only the endothelial cells in the subpapillary plexus were stained. There were many HLA-DR+T lymphocytes in lesional and non-lesional dermis. In the epidermis, HLA DR was detected only in lesional keratinocytes and T lymphocytes.
CONCLUSION
These results suggest (1) participation of activated epidermal CD8+ T lymphocytes in the formation of psoriatic plaques, and (2) a pathogenetic role of ICAM-1 expression on papillary microvessels.