As with CCR7, we showed previously that the level of CD38 expression does not correlate Erlotinib datasheet with chemotaxis towards CCL19 . Nevertheless, we could see that DC stimulated with bromelain
or with bromelain in combination with the cytokine cocktail without PGE2 had noticeably higher MFI values for CD38 (Fig. 2B). Addition of reduced amounts of PGE2 did not increase the MFI. Thus, PGE2 had an inhibitory effect of CD38 expression on DC, similar to IL-12p70 production. Interestingly, a correlation between CD38 expression and IL-12p70 secretion of DC has been described previously , in agreement with our data. The only DC population capable of producing higher amounts of IL-12p70 was DC stimulated PS-341 nmr with bromelain in combination with the cytokine cocktail without PGE2. We expected to find a higher secretion of IL-12p70 in the group stimulated with the cytokine cocktail without PGE2, as PGE2 has been claimed to be responsible for the lack of this cytokine, but our results indicate that it is not enough to only remove PGE2. In addition to not producing any notable amounts of IL-12p70, these DC also showed a less mature phenotype compared with the other groups, so obviously PGE2 is necessary for inducing (phenotypic) maturation. However, addition of bromelain could overcome this lack of stimulation. On the other hand, bromelain alone was not potent enough to induce both phenotypic
maturation and high IL-12p70 production. The lack of IL-12p70 production was not a result of a general inability of the DC, as we detected large amounts of IL-12p70 after stimulation with the bacterial compound OK432
using DC from the same preparation . Comparing the functionality of the generated DC populations in a MLR, we could show that PGE2 also influenced the T cell stimulatory capacity of the DC. When DC stimulated with the modified cytokine cocktail without PGE2 were cocultured with lymphocytes, fewer proliferative T cells were detected. Addition of ¼ of PGE2 to the cocktail improved this stimulatory capacity. This was also true regarding the phenotype of the cells. Use of ¼ of the amount of of PGE2 in the cocktail increased the expression of surface maturation markers, and some markers had even higher surface expression using this stimulation than with the original cytokine cocktail. Addition of bromelain to both the original and the modified cytokine cocktail with reduced PGE2 resulted in an even more mature phenotype, but this phenotype had an insufficient secretion of IL-12p70. Because IL-12p70 is essential for a strong induction of cytotoxic T lymphocyte (CTL) responses, several other attempts to generate DC with high IL-12p70 secretion have been made by other research groups. Stimulation with polyriboinosinic polyribocytidylic acid (poly I:C) has shown to generate DC capable of producing high amounts of IL-12p70 [34, 35].