The effects of CD8+γδ T cells on late allergic airway responses and airway inflammation in rats

Background: Gamma-delta (gammadelta) T cells regulate immune responses to foreign protein at mucosal surfaces. Whether they can modify allergen-induced early (EAR) and late airway responses (LAR) is unkown. Objective: We have tested the hypothesis that the CD8(+) sub-type of gammadelta T cells decreases allergen-induced LAR and airway eosinophilia in the rat. Methods: Brown Norway rats were administered, intraperitoneally, 3.5 x 10(4) lymph node CD8(+)gammadelta T cells from naive or sensitized rats. The recipients were sensitized to ovalbumin (OVA) in Al(OH)(3) 3 days after cell transfer and challenged with aerosolized OVA 14 days later. Serum IgE was measured before allergen challenge. After challenge, lung resistance was monitored for 8 hours and then bronchoalveolar lavage (BAL) was analyzed for eosinophil major basic protein (MBP), IL-4, IL-5, IL-13, and IFN-gamma messenger RNA-expressing cells. Results: gammadelta T cells from naive donors significantly decreased LAR in OVA-challenged sensitized rats, whereas MBP+ eosinophils were decreased by both gammadelta T cells from naive and sensitized donors. EAR and serum IgE levels were unchanged. The expression of IL-4, IL-5, and IL-13 by BAL cells of gammadelta T cell recipients was attenuated compared with OVA-challenged controls. This was accompanied by an increase in the expression of IFN-gamma. Conclusions: Our results are consistent with a suppressive role of CD8(+)gammadelta T cells on allergic airway responses. However, only gammadelta T cells from naive donors inhibit LAR.