PROPAGATION OF DENDRITIC CELL PROGENITORS FROM NORMAL MOUSE-LIVER USING GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR AND THEIR MATURATIONAL DEVELOPMENT IN THE PRESENCE OF TYPE-1 COLLAGEN

Within 1 wk of liquid culture in granulocyte/macrophage colony-stimula ting factor (GM-CSF), normal B10 BR (H-2(k) I-E(+)) mouse liver nonpar enchymal cells (NPC) formed loosely adherent myeloid cell clusters tha t have been shown to contain dendritic cell (DC) progenitors in simila r studies of mouse blood or bone marrow. Mononuclear cell progeny rele ased from these clusters at and beyond 4 d exhibited distinct dendriti c morphology and were actively phagocytic. After 6-10 d of culture, th ese cells strongly expressed CD45, CD11b, heat stable antigen, and CD4 4. However, the intensity of expression of the DC-restricted markers N LDC 145, 33D1, and N418, and the macrophage marker F4/80, intercellula r adhesion molecule 1, and Fc gamma RII was low to moderate, whereas t he cells were negative for CD3, CD45RA, and NK1.1. Splenocytes prepare d in the same way also had a similar range and intensity of expression of these immunophenotypic markers. Unlike the splenic DC, however, mo st of the GM-CSF-propagated putative liver DC harvested at 6-10 d expr essed only a low level of major histocompatibility complex (MHC) class II (I-E(k)), and they failed to induce primary allogeneic responses i n naive T cells, even when propagated additionally in GM-CSF and tumor necrosis factor alpha and/or interferon gamma-supplemented medium. Ho wever, when 7-d cultured GM-CSF-stimulated liver cells were maintained additionally for three or more days on type-1 collagen-coated plates in the continued presence of GM-CSF, they exhibited characteristics of mature DC: MHC class II expression was markedly upregulated, mixed le ukocyte reaction stimulatory activity was increased, and phagocytic fu nction was decreased. Similar observations were made when Ia(+) cells were depleted from the GM-CSF-propagated cells before exposure to coll agen. Further evidence that the GM-CSF-stimulated class IIdim or class II-depleted hepatic NPC were immature DC was obtained by injecting th em into allogeneic B10 (H-2(b) I-E(-)) recipients. They ''homed'' to T cell-dependent areas of lymph nodes and spleen where they strongly ex pressed donor MHC class II antigen 1-5 d later These observations prov ide insight into the regulation of DC maturation, and are congruent wi th the possibility that the migration of immature DC from normal liver and perhaps other organ allografts may help explain their inherent to lerogenicity.