Background Traditionally, immunological responses have been studied in-vitro whereby immune cells are subject to certain stimuli following which alterations in RNA and/or protein expression are measured. Recently, we have challenged this model by showing that mast cells (cells specialised in allergic reactions) triggered repeatedly through their Ig Fc epsilon receptor undergo a reprogramming of their responses (Suurmond et al. JACI, 2016). The differential expression of genes upon a single trigger were dampened and de-novo transcribed genes were observed. The latter belonged to the antigen presentation and pathogen defence response pathways implying a dramatic change in the cellular response mode. We have now extended this work by challenging mast cells with plate-bound IgG in a repeated mode, a model relevant for arthritic diseases where mast cells and IgG immune complexes are likely to interact.
Materials and methods Human cord blood-derived mast cells were treated for 2 weeks with plate-bound IgG. The expression profile of naive or treated mast cells was measured through RNA sequencing, quantitative RT-PCR, flow cytometry. Protein secretion was measured with ELISA and Luminex assays. Metabolic changes were measured using HPLC mass-spectrometry.
Results Similar to our previous work on Fc Epsilon receptor, we observe a dampening of the normal IgG responses with a set of novel genes upregulated. Interestingly, de-novo expressed genes consisted of DHCR7 and DHCR24, key enzymes in the cholesterol pathway. Pathway analysis confirms an enrichment of genes in this pathway following repeated IgG triggering. Preliminary data on metabolic profiling reveals a decrease in phospholipid levels in repeatedly activated mast cells.
Conclusions Our study provides evidence that mast cells are also reprogrammed upon repeated IgG triggering. In contrast to repeated Fc Epsilon Receptor triggering, different pathways are affected, implying stimulus-specific effects. Our work has important implications for revisiting the traditional immunological models in the (in-vitro) modelling of chronic (arthritic) diseases.
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