Identification of Functional Peanut-Responsive Tregs in Peanut Allergic Human Blood
Sunday, March 6, 2016: 2:15 PM
Room 406AB (Convention Center)
David Chiang, MS, ,
Rationale: The presence and suppressive capacity of food-allergen specific regulatory T cells in humans remains poorly understood.

Methods: Blood was obtained from peanut allergic (n=15) or control (n=6) subjects. PBMCs were evaluated by flow cytometry. CD25+ cells were removed by magnetic depletion or Tregs were selectively depleted by FACS, and cells were stimulated with peanut extract or staphylococcal enterotoxin B (SEB). Measured outcomes included activation (CD154, 6-18hrs), proliferation (Ki67, 5 days), and cytokine secretion (5 days).

Results: Stimulation of PBMCs from allergic but not healthy subjects with peanut resulted in upregulation of CD154 on Foxp3+CD25+CD127lowcells. CD25 depletion prior to peanut stimulation abolished the appearance of CD154+ Tregs, indicating that these cells were derived from the CD25+ population at baseline. Removal of Tregs by CD25 or FACS resulted in suppressed proliferative responses to peanut, indicating that Tregs contribute to the proliferating pool of cells after peanut stimulation. CD25 depletion led to significant increases in peanut-induced IFNγ, TNFα, IL-21, and IL-6, whereas surprisingly there were significant decreases in peanut-induced Th2 cytokines – IL-5, IL-9, and IL-13. Similar patterns were observed with SEB stimulation. Immune profiling of CD25-depleted PBMCs demonstrated depletion of basophils as well as Tregs. Selective Treg-depletion by FACS led to increased Th1 and Th2 cytokine responses to peanut.

Conclusions: Our data demonstrate the presence of functional peanut-responsive Tregs in peripheral blood of peanut allergics, but not healthy controls. Our data also demonstrate that basophils, but not Tregs, contribute substantially to the production of Th2 cytokines central to the pathogenesis of food allergy.