Basophils as a primary inducer of the T helper type 2 immunity in ovalbumin‐induced allergic airway inflammation

Abstract

SummaryAntigen-induced allergic airway inflammation is mediated by T helper type 2 (Th2) cells and their cytokines, but the mechanism that initiates the Th2 immunity is not fully understood. Recent studies show that basophils play important roles in initiating Th2 immunity in some inflammatory models. Here we explored the role of basophils in ovalbumin (OVA) -induced airway allergic inflammation in BALB/c mice. We found that OVA sensitization and challenge resulted in a significant increase in the amount of basophils in blood and lung, along with the up-regulation of activation marker of CD200R. However, depletion of basophils with MAR-1 or Ba103 antibody attenuated airway inflammation, represented by the significantly decreased amount of the Th2 subset in spleen and draining lymph nodes, interlukin-4 level in lung and OVA-special immunoglobulin E (sIgE) levels in serum. On the other hand, adoptive transfer of basophils from OVA-challenged lung tissue to naive BALB/c mice provoked the Th2 immune response. In addition, pulmonary basophils from OVA-challenged mice were able to uptake DQ-OVA and express MHC class II molecules and CD40 in vivo, as well as to release interleukin-4 following stimulation by IgE-antigen complexes and promote Th2 polarization in vitro. These findings demonstrate that basophils may participate in Th2 immune responses in antigen-induced allergic airway inflammation and that they do so through facilitating antigen presentation and providing interleukin-4.

Basophil-associated OX40 Ligand Participates in the Initiation of Th2 Responses during Airway Inflammation

“…Numerous studies have demonstrated that basophils not only play crucial roles in the effector phase, but also critically participate in the initiation of Th2-centered immune responses (7)(8)(9)(10)(11). Using an ovalbumin (OVA)-induced allergic airway inflammation mouse model, we previously showed that basophils acted as a primary inducer of the Th2 immunity, evident by increased OVA-specific immunoglobulin E (OVA-sIgE) and IL-4 levels both in serum and bronchial alveolar lavage fluid (BALF), and increased proportion of Th2 cells in the spleen after transfusion of lung basophils derived from OVA-challenged mice into wild-type (WT) mice (12). We also found that pulmonary basophils were capable of antigen uptake, expressed an array of molecular markers such as CD40, CD80/86, and MHC II and released high levels of IL-4 following OVA sensitization and challenge.…”

“…For the initiation of Th2 cells, BM-Bas (2.5 ϫ 10 5 per well) and naïve CD4 ϩ T cells (5 ϫ 10 5 per well) were seeded in 96-well plates in RPMI 1640 complete medium in the presence of rIL-2 (20 U/ml, R&D Systems), rIL-3 (30 ng/ml), DNP-OVA (100 g/ml, Biosearch Technologies, Novato) and anti-DNP IgE (10 g/ml, Sigma-Aldrich) for 5 days (7,12). For some experiments, anti-mouse CD252 (20 g/ml, OX40L blocking Ab, ␣OX40L, eBioscience) was added to the cultures.…”

“…ELISA-Cell-culture supernatants, BALF, serum and mediastinal lymph nodes (MLN) lysate supernatants were prepared as described previously (12). The levels of IL-4, IL-5, and IL-13 were measured with sandwich ELISA kits (eBioscience) according to the manufacturer's instructions.…”

“…The levels of IL-4, IL-5, and IL-13 were measured with sandwich ELISA kits (eBioscience) according to the manufacturer's instructions. For the measurement of serum OVA-sIgE, standard mouse OVA-specific IgE and anti-mouse IgE (Serotec, U.K.) were used as described previously (12).…”

“…2.5 ϫ 10 5 purified MLN basophils from immunized mice were transferred twice into recipient mice (WT C57BL/6 mice or OX40 Ϫ/Ϫ mice) at 14-day intervals (day 0 and 14) according to the protocols as described previously (7,12). Recipient mice were challenged i.n.…”