Antigen Processing by Rat Lymph-Borne Dendritic Cells

Abstract

The central function of dendritic cells (DC) is to present antigen to T lymphocytes (Reviewed in¹). Several groups have shown that DC in peripheral tissues can capture antigens and can present them to sensitized T cells “in vitro” or to naive T cells “in vivo”^2–4. We have shown that antigens injected into the small intestine or given by gavage are captured by DC in the intestinal wall and transported in lymph, and that such DC can prime naive T cells^5,6. Studies of murine LC show that cells freshly isolated from epidermal sheets are very weak stimulators of resting T cells in the MLR, but are active antigen-processing cells and can present antigens to T cell lines. After culture “in vitro” however, they dramatically increase their ability to stimulate a MLR but lose the ability to process native antigen although their ability to present peptides is maintained^7,8. A hypothesis which accommodates these observations is that peripheral DC acquire antigen locally but are unable to activate resting T cells in their vicinity, and travel to secondary lymphoid organs. Here, as they are unable to process fresh antigen, they retain an “image” of the antigens they acquired in the periphery and can present them to resting T cells.