CD103+ DCs (dendritic cells) and CCR9+ pDCs (plasmacytoid DCs) have been implicated in promoting tolerance to antigens through regulatory-T cell induction. We have conducted food oral immunotherapy (OIT) clinical studies for the last 3 years at Stanford University. We hypothesized that subjects with food allergies have low CD103+ and CCR9+ expression on their DCs but that these DC populations change over time while on therapy.
OIT was conducted and blood samples were drawn at baseline and approximately every 5 months during the study. The study is currently ongoing. PBMCs (peripheral blood mononuclear cells) were purified and flow cytometry was performed on gated DCs (LSRII, BD Biosciences).
DCs expressing CD103 (integrin-alpha E) and CCR9 (CCL25 chemokine receptor) were examined in three cohorts - (1) patients undergoing milk or peanut OIT (n=8), (2) healthy controls (HC) (n=8), and (3) non-OIT food allergy patients (FA) (n=8). PBMCs were incubated for 6 or 18 hours either with or without offending allergen. CCR9+ expression on pDCs was significantly greater in HC versus FA patients (42%±25% vs 11%±10%; p <0.01) while CD103 expression on DCs was comparatively greater in HC versus FA patients (0.19%±0.17% vs 0.07%±0.07%; p=0.16). After offending allergen stimulation for both 6 and 18 hours, CCR9 presence on pDCs significantly increased more in FA patients than in HC patients (213MFI*-6hr, 188MFI-18hr versus 12MFI for HC; p<0.03). In OIT patients, CCR9 change on pDCS after stimulation was significantly different than their baseline CCR9 MFI shift values (16MFI versus 188MFI; p<0.03) and more in line with the HC profile. *-Median Fluorescent Intensity.
The CCR9 and CD103 DC populations may play an important role for food allergy patients undergoing OIT. These tolerogenic DC changes in OIT may reveal one way that regulatory T-cell mediated tolerance, T-cell anergy, and/ or clonal deletion is induced.