Objective To compare the immunological characteristics of T cell receptor (TCR) repertoire between peripheral blood and pleural effusion in patients with lung cancer.

Methods Peripheral blood and pleural effusion samples were collected from 5 lung cancer patients with malignant pleural effusion hospitalized in Zhongshan Hospital, Fudan University from July 2020 to January 2021. Peripheral blood mononuclear cells (PBMC) and pleural effusion mononuclear cells (PEMC) were isolated, and genomic DNA was extracted. The diversity and other characteristics of TCR repertoire were analyzed.

Results There were no significant differences in the diversity and correlation of TCR clonotypes, VJ pairs and complementarity determining region 3 (CDR3) sequences between PBMC and PEMC. The number of TCR clones detected in PBMC was significantly higher than that in PEMC (P < 0.05). The numbers of VJ pairs and CDR3 were not significantly different between PBMC and PEMC. The ratio of the number of shared VJ pairs to the total VJ pairs was higher than the ratio of the number of shared clonotypes and CDR3 sequences in PBMC and PEMC paired samples (P < 0.05), and the latter two were not significantly different. Both the number and proportion of highly expanded clones (HEC) in PEMC were higher than those in PBMC. Thirty-six VJ pairs that were differentially expressed between PBMC and PEMC were also identified, 25 of which were increased and 9 were decreased in PEMC.

Conclusions The TCR repertoire in peripheral blood and pleural effusion in lung cancer patients showed different characteristics. TCR repertoire is of great significance to understand the immunopathological characteristics of lung cancer.