Interferon-γ-dependent inhibition of late allergic airway responses and eosinophilia by CD8+γδ T cells

We have previously shown that CD8(+)gamma delta T cells decrease late allergic airway responses, airway eosinophilia, T helper 2 cytokine expression and increase interferon-gamma (IFN-gamma) expression. We hypothesized that the effects of CD8(+)gamma delta T cells were IFN-gamma mediated. Brown Norway rats were sensitized to ovalbumin on day 1. Cervical lymph node CD8(+)gamma delta T cells from sensitized animals were treated with antisense oligodeoxynucleotide (5 mu mol/l) to inhibit IFN-gamma synthesis or control oligodeoxynucleotide and 3.5 x 10(4) CD8(+)gamma delta T cells were injected intraperitoneally into sensitized recipients on day 13. Rats were challenged with aerosolized ovalbumin on day 15 and lung resistance was monitored over an 8 hr period, after which bronchoalveolar lavage was performed. Control oligodeoxynucleotide treated gamma delta T cells decreased late airway responses and eosinophilia in bronchoalveolar lavage. There was a complete recovery of late airway responses and a partial recovery of airway eosinophilia in recipients of antisense oligodeoxynucleotide treated cells. Macrophage ingestion of eosinophils was frequent in rats administered gamma delta T cells but reduced in recipients of antisense oligodeoxynucleotide treated cells. These results indicate that CD8(+)gamma delta T cells inhibit late airway responses and airway eosinophilia through the secretion of IFN-gamma. Defective or altered gamma delta T-cell function may account for some forms of allergic asthma.