Integrins alpha4beta7 and alphaEbeta7 are expressed on epidermotropic T cells in cutaneous T cell lymphoma and spongiotic dermatitis.

Integrin alpha4beta7 has been associated with tissue-specific homing of malignant and inflammatory lymphocytes to gastrointestinal mucosa, whereas integrin alphaEbeta7 has been associated with intraepithelial lymphocytes in both the gut and the skin. This prompted us to examine the expression of alpha4beta7 on skin-infiltrating lymphocytes in 12 cases of patch/plaque stage cutaneous T cell lymphoma (CTCL) and in 4 cases of spongiotic dermatitis, which also display intraepidermal T cell accumulation. alpha4beta7 was found to be expressed on 64.8+/-7.4% of intraepidermal and 39.1+/-5.0% of intradermal T lymphocytes in CTCL. There was a significant positive correlation (r=0.58) between the degree of epidermotropism and the percentage of intraepidermal T cells expressing alpha4beta7. Similar findings were observed in spongiotic dermatitis, indicating that this result is not unique to malignant T cells. We evaluated staining of T cells in the same specimens for presence of alphaEbeta7 and observed a strong correlation between the expression of both beta7 integrins in each specimen. Staining with antibodies directed against the known ligands of alpha4beta7 was also performed on skin biopsies from CTCL patients. There was significantly increased dermal microvascular endothelial expression of vascular cell adhesion molecule-1 in lesional compared with nonlesional skin, and in nonlesional skin compared with skin of normal control subjects. Dermal and epidermal expression of the CS-1 domain of fibronectin was present but not increased in lesional biopsies compared with nonlesional or normal controls, whereas expression of mucosal addressin cell adhesion molecule-1 was not detectable in any skin biopsy specimens. In summary, alpha4beta7, like alphaEbeta7, is expressed at high levels on epidermotropic T cells and may interact with endothelial cell vascular cell adhesion molecule-1 as part of stepwise recruitment of lymphocytes from the blood to the epidermis.