Detection of identical T cell clones in peritumoral pleural effusion and pneumonitis lesions in a cancer patient during immune-checkpoint blockade

Abstract

Although immune-related adverse events (irAEs) of treatment with immune-checkpoint inhibitors may be due to cellular immunity mediated by T lymphocytes, their pathogenesis has remained unknown. Here we collected bronchoalveolar lavage fluid (BALF) from a cancer patient with nivolumab-induced pneumonitis and isolated mononuclear cells for next-generation sequencing of the complementarity-determining region of the T cell receptor (TCR) β chain. Mononuclear cells in peritumoral pleural effusion isolated from the patient were similarly analyzed, and the results obtained for the two specimens were compared. A substantial number of TCRβ clones in BALF were also identified among lymphocytes in the peritumoral pleural effusion. Such a correlation was not apparent between TCRβ clones in BALF and those in peripheral blood. Moreover, many tumor-associated clones with a read frequency of ≥0.10% were also present in BALF. Our data suggest that irAEs might be induced by drug-activated lymphocytes originating from tumor tissue. Deep sequencing will thus be indispensable for investigations of the immune-based pathogenesis of, and the development of optimal treatments for, irAEs.

Keywords: bronchoalveolar lavage fluid; complementarity-determining region; immune-checkpoint inhibitor; immune-related adverse event; next-generation sequencing.

Figure 1. Chest CT scans of the patient

(A) Clinical course of the pleural effusion and metastatic tumors. (B) Clinical course of the pneumonitis.

Figure 2. Flow cytometric analysis of lymphocyte subsets in BALF, pleural fluid, and peripheral blood of the patient

(A, B) Expression of CD19 and CD3 on CD45⁺ cells (A) and expression of CD4 and CD8 on CD45⁺ CD3⁺ cells (B) in BALF. (C–E) Expression of PD-1 and TIM-3 on CD8⁺ T cells and CD4⁺ T cells in pleural fluid (C), BALF (D), and peripheral blood (E). (F) Expression of PD-1 and TIM-3 on CD8⁺ T cells and CD4⁺ T cells in BALF of patients with secondary organizing pneumonia (OP) or drug-induced pneumonitis.

Figure 3. Relations among the numbers of TCRβ clones in pleural fluid, BALF, and peripheral blood of the patient

(A–C) Numbers of clones in BALF and pleural effusion (A), in pleural effusion and peripheral blood (B), and in BALF and peripheral blood (C). Pearson’s correlation coefficient (r) values are shown. (D) T cell clones in BALF (read frequency of ≥0.1%) compared with those detected in pleural fluid. (E) T cell clones in peripheral blood (read frequency of ≥0.1%) compared with those detected in pleural fluid. (F) T cell clones in BALF (read frequency of ≥0.1%) compared with those detected in peripheral blood. X and Y axis indicate each clone of TCRβ and read frequency, respectively.