e20053 Background: Immune repertoire (IR) is the collection of functionally diverse T and B cells in an individual's circulatory repertoire at a particular time. The CDR3 is the main variation region of the CDR of T cell receptors (TCRs), which directly determines the antigen specificity of the receptor. The purpose of this study was to investigate the differences in TCRs between tumor patients and healthy people by using NGS sequencing of the CDR3 region of the human TRB. Shannon indices and Simpson indices were used to evaluate the TCR richness and evenness. Methods: From 2018 to 2022, a total of 537 cases of lung adenocarcinoma and 85 cases of healthy individual PBMC in China were collected. We identified 59 V and 14 J genes in the TRB CDR3 region by amplicon sequencing, and analyzed the differences between Shannon_index and simpson index. Results: TCR diversity were significantly higher in healthy people compared to lung adenocarcinoma patients as determined by Shannon index analysis ( P = 0.006), and the uniformity of TCRs in the latter group was lower (Simpson index 0.997 and 0.992 for controls and cases, respectively). For different age groups of lung cancer patients (age 20-44, n = 66; age 45-59, n = 205; age 60-74, n = 221; age 75-90, n = 45), the overall abundance and uniformity of T cells in lung cancer patients decreased with the increase of age (Shannon index: 7.91, 7.63, 7.38, 6.99, respectively. Simpson Index: 0.996, 0.994, 0.991, 0.986 respectively). The downward trend in the Shannon index between healthy individuals and lung adenocarcinoma patients exhibit a high correlation (spearman r = 1, P < 0.01), indicating that age rather than cancer may be the main factor in immune decline in patients with lung adenocarcinoma. In terms of gender, the abundance and uniformity of T cell types in male patients were lower than that in female patients (male: Shannon index = 7.36, Simpson index = 0.991; Female: Shannon index = 7.61, Simpson index = 0.994), suggesting higher levels of immunity in the female patients. Conclusions: The Shannon index (immune diversity) in TCR sequencing was significantly different between lung adenocarcinoma patients and healthy individuals. In patients with lung adenocarcinoma, immunity declines more due to aging than the cancer itself. TCR diversity was lower in male lung adenocarcinoma patients than in female patients. In conclusion, Shannon index (immune diversity) in TCR sequencing can be used as a predictor of lung adenocarcinoma.