The mode of protein antigen administration determines preferential presentation of peptide-class II complexes by lymph node dendritic or B cells.

We have compared the capacity of dendritic cells (DC) and B cells to present peptide-class II complexes following administration of protein in adjuvant or in soluble form. Three different antigen-presenting cell (APC) populations were separated from draining lymph node cells from mice immunized s.c. with hen egg-white lysozyme (HEL) in adjuvant or with adjuvant only followed by soluble HEL: DC (N418+, class II+, B220-, low buoyant density), large B cells (B220+, low buoyant density) and small B cells (B220+, high buoyant density). HEL peptide-class II complexes displayed by these APC were evaluated by their capacity to activate HEL-specific T hybridoma cells. Following immunization with HEL in adjuvant, DC are the only lymph node APC population expressing detectable HEL peptide-class II complexes. Conversely, after i.v. administration of soluble HEL in mice previously injected with adjuvant only, lymph node B cells are much more efficient than DC in presenting peptide-class II complexes to T cells. Therefore, different modes of protein antigen administration lead to selective expression of antigenic complexes by different APC populations. These data correlate with the observation that, unlike B cells, DC recruited in lymph nodes of mice injected with adjuvant only present in vitro processed protein antigen much less efficiently than synthetic peptides, probably as a consequence of their maturation in vivo.