A Newly Identified Antigen Retention Compartment in the FSDC Precursor Dendritic Cell Line

Abstract

Antigen uptake and presentation by dendritic cells (DC) occur at different stages of their maturation and are directed by certain cytokines (1–3). Phagocytosis (4) as well as mannose receptor-mediated endocytosis through clathrin-coated pits and fluid-phase macropinocytosis have been described for human and murine DC at the immature developmental stage (5, 6). Antigen presentation capacity of those cells is weak. After antigen contact with an atnigen or proinflammatory cytokines they mature under loss of the antigen uptake capabilities, but upregulate surface MHC class II and costimulatory molecules for antigen presentation. In vivo, resting DC of non-lymphoid organs internalize antigens and transport them to the draining lymph nodes. In the T cell areas of the lymph node the now fully mature interdigitating DC is able to initiate primary T cell responses. During migration the DC undergoes maturation, but antigen processing should be delayed until it reaches the lymph node. In the precursor DC line FSDC (6, 7), we have now identified a specialized antigen retention compartment, and propose a mechanism of how antigens within these vesicles are prevented from degradation by lysosomal enzymes.