DEPLETION OF CD8(-CELLS ENHANCES PULMONARY INFLAMMATION BUT NOT AIRWAY RESPONSIVENESS AFTER ANTIGEN CHALLENGE IN RATS() T)

Background: CD8(+) (OX-8(+)) T cells may suppress airway inflammation and airway responsiveness after allergen challenge. Objective: We stud ied the effects of depletion of OX-8(+) T cells on allergen-induced lu ng eosinophilia and airway responsiveness in the Sprague-Dawley rat.Me thods: Sprague-Dawley rats were sensitized to ovalbumin and challenged by aerosol 14 days later. Test animals received either low-dose (2 mg , n = 9) or high-dose (3 mg, n = 7) OX-8 monoclonal antibody (mAB), wh ereas controls (n = 8) received BALB/c ascites fluid. A fourth group o f animals (n = 10) was not sensitized to ovalbumin and also received a scites fluid. Twenty-four hours after ovalbumin challenge, responsiven ess to methacholine was measured, and lung inflammation was assessed i n the large airways and small airways and parenchyma. Results: Circula ting and airway CD8(+) T cells were decreased by OX-8 mAB administrati on with greatest changes in animals treated with high-dose OX-8 mAB co mpared with controls (blood: 1.0% +/- 3.6% vs 18.7% +/- 3.9%, p < 0.05 ); (large airways: 2.5% +/- 1.2% vs 13.8% +/- 1.2%, p < 0.05). Ovalbum in challenge resulted in increases in macrophages and neutrophils in t he small airways and parenchyma of sensitized compared with unsensitiz ed rats (p < 0.05). High-dose OX-8 mAB further increased total leukocy tes, attributable to increases in neutrophils and eosinophils, retriev ed from the large airways and small airways and parenchyma compared wi th other groups (p < 0.05). Airway responsiveness to methacholine was not significantly different between control and ovalbumin-challenged a nimals and was not augmented by OX-8 pretreatment. Conclusion: CD8(+) T cells modulate the extent of allergen-induced airway inflammation. H owever, the enhancement of inflammation was not sufficient to affect a irway responsiveness.