Phenotypic alterations and IL-1β production in CD34+ progenitor- and monocyte-derived dendritic cells after exposure to allergens: a comparative analysis

Dendritic cells (DC) have been shown to capture and process antigens and play an initiating role in contact sensitization. Cells with dendritic morphology can be generated in vitro either from CD34+ cord blood cells or from CD14+ peripheral monocytes. The aim of this study was to determine the state of maturation/activation of both populations after exposure to several concentrations of four well-established model allergens (nickel sulfate, eugenol, α-hexylcinnamaldehyde and 2,4,6-trinitrobenzene sulfonic acid) or the irritant sodium dodecyl sulfate. We analyzed the surface expression of CD86, CD83 and HLA-DR and the production of IL-1β. DC from the two sources were generated separately in two laboratories, but challenged using identical test protocols. Using both DC populations it was possible to detect the allergens under investigation, though minor differences regarding effective concentrations were noted. The non-responsiveness of CD34-DC to CIN was probably due to non-optimal concentrations. Ni2+, known as a moderate allergen in vivo, showed the most prominent effect in both cell systems. CD86 expression was the most reliable phenotypic marker for the in vitro identification of allergens. Due to substantial individual variations it was difficult to draw any definite conclusions as to the relevance of IL-1β production as an activation endpoint. We conclude that both test systems are able to respond to allergens, but CD34-DC must be exposed to higher concentrations to demonstrate significant phenotypic changes. On the other hand, Mo-DC from only some of the donors reacted to allergens, in contrast to CD34-DC, which responded to allergens irrespective of the donor, thus necessitating the use of Mo-DC cultures from several blood donors.