Methods: Human plasmacytoid DC (pDC) expressing FcER1+ were sensitized with TMA-IgE sensitized workers' sera (n=2) at a 1:20 dilution, washed and exposed to either (a) HSA; (b) free TMA or; (c) an LPS-free TMA-HSA conjugate. Cells were harvested and analyzed by RNA sequencing. Unexposed DCs or DCs incubated with non-TMA exposed control sera served as additional controls. Differentially expressed genes (DEGs; adjusted p-values <0.05) were used for bioinformatic analyses.
Results: Free TMA exposure associated-DEGs involved innate immunity and cell migration pathways including IL23A, IL15, epiregulin and endothelin. In contrast, TMA-HSA exposure was associated with DEGs involved in humoral immune responses including SORBS1, TNFSF13B, CD300LB and LYN tyrosin kinase. Pathway analyses revealed over-representation of Granzyme B pathway genes and inflammatory immune genes for the free TMA and TMA-HSA groups, respectively. Specific cytokines (IL1, IL6) and chemokines (CCL4, CCL20) were upregulated in both groups.
Conclusions: Gene expression of pDCs exposed to free TMA is distinctly different from pDCs exposed to TMA-HSA. Real-time PCR studies are in progress to more precisely understand these findings.