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 p resent peptide-class II complexes following administration of protein in adjuvant or in soluble form, Three different antigen-presenting cel l (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+, B2 20(-), low buoyant density), large B cells (B220(+), low buoyant densi ty) and small B cells (B220(+), high buoyant density), HEL peptide-cla ss II complexes displayed by these APC were evaluated by their capacit y to activate HEL-specific T hybridoma cells, Following immunization w ith HEL in adjuvant, DC are the only lymph node APC population express ing detectable HEL peptide-class II complexes, Conversely, after i.v. administration of soluble HEL in mice previously injected with adjuvan t only, lymph node B cells are much more efficient than DC in presenti ng peptide-class II complexes to T cells, Therefore, different modes o f protein antigen administration lead to selective expression of antig enic 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 an tigen much less efficiently than synthetic peptides, probably as a con sequence of their maturation in vivo.