T cell-mediated terminal maturation of dendritic cells, a critical transition into fully potent antigen presenting cells.

Dendritic cells (DC) are a special subset of leukocytes characterized by their potent ability to activate immunologically naive T cells. We established a series of long-term DC lines, termed "XS lines", from the epidermis of newborn mouse skin. These lines retain many important features of resident DC in epidermis, i.e., Langerhans cells (LC), including surface phenotype, antigen (Ag) presenting capacity, and cytokine and cytokine receptor profiles. Working with XS lines, we have observed recently that DC undergo rapid and profound changes during Ag presentation. Specifically, upon Ag-specific interaction with T cell clones, XS52 cells: a) begin to secrete several cytokines (IL-1 beta, IL-6, and TNF alpha), b) lose the expression of CSF-1 receptor and proliferative responsiveness to CSF-1, c) elevate the expression of B7-2 (CD86), and d) lose the phagocytotic and adhesive capacities. We propose that these changes represent "T cell-mediated terminal maturation" of DC, a critical transition into a fully professional Ag presenting cell.