Multiplex immunofluorescence in the identification of immune cell compositions in rejection, bronchus-associated lymphoid tissue, and infection in lung allograft tissue.

Spatial immune cell profiling using multiplex immunofluorescence was examined to characterize the inflammatory cell infiltrates and to possibly aid in the distinction of acute cellular rejection (ACR) and lymphocytic bronchiolitis (LB) from its mimickers including bronchus-associated lymphoid tissue (BALT) and infection in lung allograft tissue. Lung allograft biopsies with ACR and/or LB were identified from an institutional pathology lung transplant database (2012-2024). Surgical lung specimens, transbronchial biopsies, and autopsy lungs were used for BALT and infection, respectively. Multiplex immunofluorescence using the PhenoCode Signature Immune Profile Human Protein Panel (CD3e, CD8, CD20, CD68, FoxP3, pankeratin) was performed. The study included tissue specimens with ACR (n = 13), LB (n = 10), BALT (n = 12), and infection (n = 13). The percentage of CD3 + T-cells, CD8 + T-cells, and CD68 + macrophages was higher and the percentage of CD20 + B-cells was lower in ACR, LB, and infection than BALT (p ≤ 0.02, all). The percentage of FoxP3 + CD3 + T-cells was higher in ACR and BALT than infection (p ≤ 0.02, all). In conclusion, ACR and LB are predominantly comprised of T-cells, however B-cells, macrophages, and FoxP3 + CD3 + T-cells are also present. The immune cell composition of ACR and LB is distinct from that of BALT but similar to infection.