Serotype-dependent response of human dendritic cells stimulated with Aggregatibacter actinomycetemcomitans

Different serotypes of Aggregatibacter actinomycetemcomitans have been described based on the lipopolysaccharide (LPS)-O-polysaccharide antigenicity. In turn, a distinct effect of A. actinomycetemcomitans serotypes has been described on cell proliferation and pro-inflammatory cytokine production in different human cells. This study was aimed to investigate the differential dendritic cell (DC) response when stimulated with different bacterial strains belonging to the most prevalent serotypes of A. actinomycetemcomitans (a-c).

Dendritic cells were obtained from healthy subjects and stimulated with increasing multiplicity of infection (MOI = 10(-1) -10(2)) of A. actinomycetemcomitans, serotypes a-c, or their lipopolysaccharide (10-50 ng/ml). The levels for interferon (IFN)-γ, tumour necrosis factor (TNF)-α, interleukin (IL)-1β, IL-5, IL-6, IL-10, IL-12 and IL-23 were quantified by real-time RT-PCR and ELISA.

Variable DC responses were detected when stimulated with the different strains of A. actinomycetemcomitans. DCs stimulated with A. actinomycetemcomitans strains belonging to the serotype b or their purified LPS expressed higher levels of IL-1β, IL-6, IL-12, IL-23, IFN-γ and TNF-α than DCs stimulated with the other serotypes.

Aggregatibacter actinomycetemcomitans strains belonging to the serotype b demonstrated a higher capacity to trigger Th1 and Th17-type cytokine production on DCs. These increased potential is likely explained by a higher immunogenicity of their LPS.