HIGH-LEVELS OF A MAJOR HISTOCOMPATIBILITY COMPLEX-II SELF-PEPTIDE COMPLEX ON DENDRITIC CELLS FROM THE T-CELL AREAS OF LYMPH-NODES

T lymphocytes recirculate continually through the T cell areas of peri pheral lymph nodes. During each passage, the T cells survey the surfac e of large dendritic cells (DCs), also known as interdigitating cells. However, these DCs have been difficult to release from the lymph node . By emphasizing the use of calcium-free media, as shown by Vremec et al. (Vremec, D., M. Zorbas, R. Scollay, D.J. Saunders, C.F. Ardavin, L . Wu, and K. Shortman. 1992. J. Exp. Med. 176:47-58.), we have been ab le to release and enrich DCs from the T cell areas. The DCs express th e CD11c leukocyte integrin, the DEC-205 multilectin receptor for antig en presentation, the intracellular granule antigens which are recogniz ed by monoclonal antibodies M342, 2A1, and MIDC-8, very high levels of MHC I and MHC II, and abundant accessory molecules such as CD40, CD54 , and CD86. When examined with the Y-Ae monoclonal which recognizes co mplexes formed between I-A(b) and a peptide derived from I-E alpha, th e T cell area DCs expressed the highest levels. The enriched DCs also stimulated a T-T hybridoma specific for this MHC II-peptide complex, a nd the hybridoma underwent apoptosis. Therefore DCs within the T cell areas can be isolated. Because they present very high levels of self p eptides, these DCs should be considered in the regulation of self reac tivity in the periphery.