Figure 1

CD4⁺T cell recognition of alveolar epithelial antigen results in airway inflammation and AEC II hypertrophy. (A) Histological examination of lungs from healthy SPC-HA (a and a'), SPC-HA six days after adoptive transfer of HA-specific CD4⁺ T cells (b, b') and SPC-HA/TCR-HA double transgenic mice (c, c'). Lung sections were stained with H&E. Black arrows indicate AEC II, red arrows indicate lymphocytes. No lesions were detectable in the lung of SPC-HA mice. Specifically, type II pneumocytes were completely unchanged (a, a'). A moderate, perivascular and peribronchiolar infiltration with mature lymphocytes was detected in the lung of SPC-HA mice after transfer with HA-specific CD4⁺ T cells. Adjacent to these infiltrations, a slight connective tissue edema and a mild infiltration with neutrophils were observed. Type II pneumocytes in the vicinity of the lymphocytic infiltrations were moderately hypertrophic. A few alveolar macrophages were present in the alveoli (b, b'). Moderate, multifocal, perivascular and peribronchiolar infiltrations with lymphocytes were present in the lung of SPC-HA/TCR-HA double transgenic mice. Type II pneumocytes close to the lymphocytic infiltrations were mildly activated and hypertrophic (c, c'). (B) Histological results were corroborated morphometrically by measuring AEC II surface and perimeter to quantify the degree of cellular hypertrophy (n = 15, 3 mice with 5 AEC II per mouse; ± standard deviation). AEC II surface: SPC-HA vs SPC-HA Transfer: P < 0,001), SPC-HA vs SPC-HA/TCR-HA (P < 0,0001), SPC-HA transfer vs SPC-HA/TCR-HA (P < 0,0001). AEC II perimeter: SPC-HA vs SPC-HA Transfer: P < 0,001), SPC-HA vs SPC-HA/TCR-HA (P < 0,001), SPC-HA transfer vs SPC-HA/TCR-HA (P < 0,001). All Student's t-test.