DIFFERENTIAL FUNCTION OF DENDRITIC CELLS ISOLATED FROM BLOOD AND LYMPH-NODES

Dendritic cells (DC) isolated from the lymph nodes or spleens of mice and pulsed with contact sensitizers or protein antigens stimulate primary proliferative responses by syngeneic T cells and responses to alloantigens in the mixed leucocyte reaction (MLR). Using enriched human peripheral blood DC, we attempted to stimulate primary immune responses to contact sensitizers by autologous lymphocytes in vitro. No significant proliferation above background levels or CD69 expression (an early activation antigen on lymphocytes) was detected despite using a wide range of donors, chemicals, antigens and cell concentrations. Culture of DC for up to 5 days in vitro in the presence of phytohaemagglutinin (PHA)-conditioned culture supernatants, or recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF) also failed to induce primary proliferative responses to contact sensitizers. Comparisons were made between blood and lymph node DC from mice to explore whether the lack of stimulation was the result of differences between mouse and human DC or between DC isolated from different tissues. DC from lymph nodes stimulated primary responses to contact sensitizers in both blood and lymph node lymphocytes whereas blood DC did not stimulate responses. Both lymph node and blood DC stimulated an allogeneic MLR, although blood DC were less efficient than those from lymph node. The data show that DC from different tissues exhibit variable functional activity. DC from blood and lymph nodes were examined to determine whether surface antigen expression is related to functional activity. Murine blood DC expressed similar levels of LFA-1, LECAM-1 and CD44 compared with lymph node DC but lower levels of MHC class II, B7 and ICAM-1. These results may therefore have important implications for antigen processing and presentation in cells from different tissue compartments.