NUCLEAR-LOCALIZATION OF RELB IS ASSOCIATED WITH EFFECTIVE ANTIGEN-PRESENTING CELL-FUNCTION

Dendritic cells (DC) are potent APCs that enter resting tissues as pre cursors and, after Ag exposure, differentiate and migrate to draining lymph nodes. The phenotype of RelB knockout mice implicates this membe r of the NF kappa B/Rel family in DC differentiation. To further eluci date the role of RelB in DC differentiation, mRNA, intracellular prote in expression, and DNA binding activity of RelB were examined in immat ure and differentiated human DC, as well as other PB mononuclear cell populations. RelB protein and mRNA were detected constitutively in lym phocytes and in activated monocytes, differentiated DC, and monocyte-d erived DC. Immunohistochemical staining demonstrated RelB within the d ifferentiated lymph node interdigitating DC and follicular DC, but not undifferentiated DC in normal skin. Active nuclear RelB was detected by supershift assay only in differentiated DC derived from either PB p recursors or monocytes and in activated B cells. These RelB(+) APC wer e potent stimulators of the MLR. The data indicate that RelB expressio n is regulated both transcriptionally and post-translationally in myel oid cells. Within the nucleus, RelB may specifically transactivate gen es that are critical for APC function.