CD8(+) T cells modulate late allergic airway responses in Brown Norway rats

To test the hypothesis that CD8(+) T cells may suppress the allergen-induce d late airway response (LAR) and airway eosinophilia, we examined the effec t of administration of Ag-primed CD8(+) T cells on allergic airway response s, bronchoalveolar lavage (BAL) leukocytes, and mRNA expression for cytokin es (IL-4, IL-5, and IFN-gamma) in OVA-sensitized Brown Norway rats. On day 12 postsensitization to OVA, test rats were administered 2 million CD8(+) T cells i.p. isolated from tither the cervical lymph nodes (LN group; n = 8) or the spleen (Spl group; n = 6) of sensitized donors. On day 14, test rat s were challenged with aerosolized OVA. Control rats were administered PBS i.p. on day 12, and challenged with OVA (n = 10) or BSA (n = 6) on day 14. The lung resistance was measured for 8 h after challenge, BAL was performed at 8 h, Cytospin slides of BAL were analyzed for major basic protein qv im munostaining and for cytokine mRNA by. in situ hybridization. The LAR was s ignificantly less in the LN group (1.8 +/- 0.5 U; p < 0.01) and BSA control s (1.4 +/- 0.7; p < 0.01), but not in the Spl group (6.7 +/- 2.2), compared with that in OVA controls (8.1 +/- 1.8). In BAL, the number of major basic protein-positive cells was lower in the LN and Spl groups compared with OV A controls (p < 0.05 and p < 0.01). IL-4- and IL-5-positive cells were decr eased in the LN group compared with the OVA controls (p < 0.01). INF-gamma- positive cells were increased in the LN and Spl groups compared with the OV A controls (p < 0.01). Serum OVA-specific IgE levels were unaffected by CD8 (+) T cell transfers, These results indicate that Ag-primed CD8(+) T cells have: a potent suppressive effect on LAR.