Effect of whole-body x-irradiation on antigen-induced airway response in sensitized guinea pigs

The objectives of this study were to test the hypothesis that x-irradiation inhibits the tate asthmatic response (LAR) without influencing the early a sthmatic response (EAR) and to examine the mechanism of the inhibitory effe ct. Twenty sensitized guinea pigs were irradiated at a dose of 8 Gy. The next d ay, one-half of the animals were injected intravenously with spleen cells ( 2 x 10(8)) collected from unirradiated sensitized guinea pigs, whilst the o ther half were injected with vehicle only. Ten additional unirradiated sens itized guinea pigs also received vehicle only. Antigen inhalation challenge took place two days later, Pulmonary resistance was measured for 6 h after antigen exposure, and bronchoalveolar lavage and lung fixation were then u ndertaken. The area under the percentage pulmonary resistance curve 2-6 h a fter allergen inhalation was used for analysis of the LAR, while the maxima l percentage change in pulmonary resistance was used for analysis of the EA R. Irradiation abolished the LAR (364.4+/-49.4 versus 62.8+/-10.4) without inh ibiting the EAR (229.3+/-27.2 versus 278.7+/-40.2) and significantly inhibi ted the accumulation of eosinophils and lymphocytes in the airways. Transfe r of spleen cells restored the LAR (334.4+/-66.8) and the recruitment of ce lls to the levels seen in unirradiated sensitized guinea pigs, In addition, transfer of only CD4+ T-lymphocytes separated from the spleen cells restor ed the LAR (439.4+/-62.1) and the cell infiltration into the airways. These inhibitory effects of x-irradiation were due to decreases in numbers of CD4+ T-lymphocytes.