FRESHLY ISOLATED MOUSE 4F7(-CELLS() SPLENIC DENDRITIC CELLS PROCESS AND PRESENT EXOGENOUS ANTIGENS TO T)

The antibody 4F7 was reported to recognize an epitope expressed on den dritic cells (DC) from various tissues. To study the ability of spleni c 4F7(+) dendritic cells to process antigen for presentation to CD4(+) T cells, DC were enriched using a separation procedure avoiding overn ight culture which could lead to an altered phenotype. These DC were u sed as antigen-presenting cells (APC) in stimulation cultures of major histocompatibility complex class II-restricted T cells. It was found that they induce antigen-dependent lymphokine production by T cells an d therefore could present exogenous antigens. These processing takes p lace intracellularly, because fixation abrogates presentation to T cel ls. Moreover, antigen presentation needs intracellular processing with in endo- or lysosomes as chloroquine-treatment prevents T cell activat ion. Titration of APC numbers revealed that contaminating APC most lik ely did not account for antigen-specific T cell activation by DC. No e vidence was found for release of antigenic peptides or for partial ant igen processing possibly done by cell surface located enzymes on DC. I n conclusion, these results indicate that freshly enriched DC are able to process antigens similarly to other APC.