Thy 1+ dendritic epidermal cells but not Langerhans cells express Ly 48

Expression of B7-1 by Pam 212 squamous cell carcinoma enhances tumor cell interactions with dendritic epidermal cells but does not affect in vivo tumor growth

Direct antigen presentation of tumor-associated antigens by tumor cells to T lymphocytes may induce clonal anergy as a mechanism of escape from immune surveillance. B7-1 is a costimulatory molecule for the activation of both CD4+ and CD8+ T lymphocytes that prevents the induction of clonal anergy. Thus, the transfer of B7-1 genes into tumor cells can induce protective immunity and lead to tumor rejection of some tumors in model systems of in vivo tumor growth; however, there is no information on whether stable expression of B7-1 can affect the in vivo growth of squamous cell carcinoma, a common skin cancer. Here, we study how the stable cell surface expression of high levels of B7-1 by Pam 212, a murine squamous cell carcinoma, affects tumor cell-lymphocyte interactions (lymphocyte proliferation and cytotoxicity). Consistent with its costimulatory role, we demonstrate that B7-1 can efficiently induce dendritic epidermal T-cell proliferation in three different dendritic epidermal T-cell cell lines. In addition, B7-1 enhances dendritic epidermal T-cell cytolytic activity against Pam 212 cells in an in vitro 51Cr-release assay, which was blocked by CTLA-4/Ig fusion protein. In contrast to dendritic epidermal T cells, the expression of B7-1 does not alter Pam 212 interactions with either cytotoxic T-lymphocytes, natural killer, or lymphokine-activated killer cells. B7-1 expression by Pam 212 cells did not alter its ability to grow tumors in vivo, as their rate of tumor growth was the same as vector-transfected Pam 212 cells, which were B7-1 negative. Our studies indicate that B7-1 gene transfer into Pam 212 does not alter its tumorigenicity, because it does not alter tumor cell-lymphocyte interactions with cytotoxic T lymphocytes, natural killer cells, and lymphokine-activated killer cells. Further studies of B7-1 modified Pam 212 and dendritic epidermal T cells will clarify whether T-cell receptor-gamma/delta-bearing T lymphocytes can play a role in immunotherapy of Pam 212 squamous cell carcinoma.

Migration of Thy-1+ dendritic epidermal cells (Thy-1+DEC): Ly48 and TNF-alpha are responsible for the migration of Thy-1+DEC to the epidermis

Thy-1+ dendritic epidermal cells (Thy-1+DEC) are mainly T cells that express T-cell receptor gamma and delta chains with limited diversity of gamma delta, mainly gamma 3 delta 1; such gamma 3 delta 1 TCR-bearing Thy-1+DEC originate from day 16 fetal thymic cells. To understand the migratory capability of Thy-1+DEC, we developed an in vitro model, using skin organ culture. First, emigration of Thy-1+DEC from the epidermis was examined. Ear skin from C3H/He mice was separated into two parts and incubated for 3 d with dermal side down. Thy-1+DEC emigrated from the epidermis into the dermis and then migrated out of the skin into the culture medium. Next, immigration of Thy-1+DEC into the epidermis was examined. Thy-1+DEC were depleted in vivo by daily application of clobetazole propionate solution topically onto the ears of C3H/He mice. Seven days later, ear skin was harvested, separated, and cultured with the dermal side up with syngeneic epidermal cell suspensions with a migration chamber for 3 d. It was found that 1) Thy-1+DEC immigrated into the Thy-1+DEC depleted epidermis as well as into untreated epidermis, and 2) the migratory capability of Thy-1+DEC was directly proved by a biolabeling technique with PKH-26. Blocking studies with various antibodies revealed that leukosialin (S11 monoclonal antibodies) and TNF alpha were important for Thy-1+DEC migration. Thus, Thy-1+DEC retain the potential for migration in vitro, and leukosialin and TNF alpha are partially responsible for the migration of Thy-1+DEC into the epidermis.