Markers of αβ T-cell–mediated immunity in simple bronchial grafts and bronchus–PLN cografts before and after infection with P aeruginosa.

Before P aeruginosa infection, the up-regulation of HLA-DR is visible in the bronchus–PLN cograft (B) compared with the simple bronchial graft (A), with strong staining of the epithelium and the mesenchymal macrophages. Before infection, few mesenchymal macrophages express CD25 (C, arrows) in the bronchus–PLN cograft, whereas BALT cells (C, circled area) are mostly CD25⁻. After in vivo infection with P aeruginosa, CD25 expression is markedly up-regulated (D, arrows) in the mesenchyme of the bronchus–PLN cograft, notably among BALT cells (D, circled area), with CD25⁺ cells spreading in the whole mucosa and the epithelium. Bar, 100 μm. e indicates epithelium; and c, cartilage. Original magnification ×100 for all panels.