Uptake of microparticle‐adsorbed protein antigen by bone marrow‐derived dendritic cells results in up‐regulation of interleukin‐1α and interleukin‐12 p40/p35 and triggers prolonged, efficient antigen presentation

Abstract

Dendritic cells synthesize and express major histocompatibility complex (MHC) class II peptide-binding elements constitutively and, therefore, belong to the category of professional antigen-presenting cells. Unlike other cells that show constitutive class II expression, such as B cells and certain T cell clones, dendritic cells possess the unique capacity to activate naive T cells. Using dendritic cells generated in vitro by culture of mouse bone marrow in the presence of low doses of recombinant mouse granulocyte/macrophage colony-stimulating factor, we found that discrete maturation stages of these cells can be distinguished which were correlated with defined functional capabilities. The striking observation was the presence of a progenitor dendritic cell expressing low levels of class II which, unlike its differentiated counterpart in vitro, possessed pronounced phagocytic activity. Adding protein antigen to dendritic cells in a particle-adsorbed form, as compared to a soluble form, we demonstrate that phagocytosis of the particle-adsorbed protein by progenitor dendritic cells involves an activation event. This is evidenced by the de novo synthesis of transcripts of interleukin-1 alpha and interleukin-12 p40/p35 as well as transcripts of MHC class II. Most importantly, an augmented and prolonged antigen-presentation capacity was observed when the antigen was given in particle-adsorbed instead of soluble form. These findings indicate that progenitor dendritic cells are functionally more flexible and potent than fully differentiated dendritic cells and that they play a crucial role in antigen presentation. It is suggested that these findings will open up new possibilities to devise strategies for vaccine development.

In vitro activation of antigen-presenting cells (APC) by defined composition of Quillaja saponaria Molina triterpenoids

“…The influenza glycoproteins in the iscom most probably mediate improved cellular adherence and increased uptake of the complexes containing the adjuvant active triterpenoids, facilitating cellular stimulation by low doses. It is also possible that the incorporation of antigen into iscoms prevents its rapid degradation in the APC, as shown with antigens adsorbed onto microparticles [26]. In addition, the viral proteins may have intrinsic capacity to stimulate cytokines, as reported earlier with influenza virus [27], and combined with matrix, or even more in the same particle-as in iscoms-a synergistic effect may be obtained.…”

Lipopolysaccharide Modulation of Dendritic Cells Is Insufficient to Mature Dendritic Cells to Generate CTLs from Naive Polyclonal CD8+ T Cells In Vitro, Whereas CD40 Ligation Is Essential

“…28 -31). Both human and murine DC have been shown to produce IL-12 in response to either microbial stimuli (32)(33)(34) or T celldependent interactions (35,18,20) in which binding of CD40 by CD40L is critical (18,20,36). Although bone marrow-derived DC have been shown to secrete IL-12p70 in response to microbial stimuli within 10 min to 24 h of stimulation (33,37), production of IL-12p70 by DC treated with aCD40 has only been reported when the DC have been stimulated for Ͼ36 h (20).…”

Vesicle Size Influences the Trafficking, Processing, and Presentation of Antigens in Lipid Vesicles

“…However, particulate Ags have also been shown to influence phagocytic APCs directly via effects on intracellular trafficking of Ag to Ag-processing compartments (12). Furthermore, the ability of particles to target Ag into phagocytic, rather than pinocytic, uptake mechanisms has also been shown to affect APC function (6,13,14).…”