DENDRITIC CELLS BUT NOT B-CELLS PRESENT ANTIGENIC COMPLEXES TO CLASS II-RESTRICTED T-CELLS AFTER ADMINISTRATION OF PROTEIN IN ADJUVANT

We have analyzed the relative contribution of dendritic cells (DC) and B cells in the presentation of peptide-class II, complexes in an infl ammatory situation in vivo. Draining lymph node cells from mice immuni zed subcutaneously with hen egg-white lysozyme (HEL) in adjuvant displ ay HEL peptide-major histocompatibility complex class II complexes abl e to stimulate, in the absence of any further antigen addition, specif ic T hybridoma cells. The antigen-presenting capacity of three differe nt antigen-presenting cell (APC) populations recruited in lymph nodes, DC (N418(+), class II+, B220(-), low buoyant density), large B cells (B220(+), low buoyant density), and small B cells (B220(+), high buoya nt density), was analyzed. After immunization with HEL in adjuvant, DC are the only lymph node APC population expressing detectable HEL pept ide-class II complexes. These results indicate that lymph node DC and not B cells are the APC initiating the immune response in vivo after a dministration of antigen in adjuvant.