Abstract
AB013. Characteristic differences in the abundance of tumor-infiltrating lymphocytes and intratumoral developing T cells in thymoma
Tatsuo Furuya, Masanori Shimomura, Satoru Okada, Chiaki Nakazono, Atsuki Uchibori, Tomoki Nishimura, Kenji Kameyama, Masayoshi Inoue
Division of Thoracic Surgery, Department of Surgery, Kyoto Prefectural University of Medicine, Graduate School of Medical Science Kyoto, Japan
Correspondence to: Tatsuo Furuya, MD, PhD. Division of Thoracic Surgery, Department of Surgery, Kyoto Prefectural University of Medicine, Graduate School of Medical Science, 465 Kajii-cho, Kamigyo-ku, Kyoto 602-8566, Japan. Email: furuya34@koto.kpu-m.ac.jp.
Background: As in the normal thymus, thymomas are frequently associated with abundant immature T cells. These intratumoral developing T cells should be distinguished from tumor-infiltrating lymphocytes (TILs) derived from peripheral blood in considering the tumor microenvironment in thymomas.
Methods: The expressions of CD4 and CD8 on T cells were analyzed by flow cytometry in 31 thymomas. The amount of T cell receptor excision circles (TRECs), which can be detected in newly formed naïve T cells in the thymus, was evaluated using sorted lymphocytes from thymomas by quantitative polymerase chain reaction (PCR). The expressions of granzyme A (GZMA) and granzyme B (GZMB) on CD8 T cells were analyzed by image cytometry using multiplex immunohistochemistry.
Results: Analyses of proportions for the CD4+CD8+ [double positive (DP)] fraction of CD3+ T cells in all types of thymomas showed that type AB, B1, and B2 (AB/B1/B2) thymomas were associated with a significantly higher proportion of DP than type A and B3 (A/B3) thymomas, similar to that of the normal thymus. The amounts of TRECs in CD4 and CD8 T cells were significantly higher in type AB/B1/B2 than in type A/B3 thymomas, and comparable to normal thymus. Both the percentages and cell densities of CD8 T cells expressing GZMA or GZMB were significantly lower in type AB/B1/B2 thymomas.
Conclusions: Most CD8 T cells in type AB/B1/B2 thymomas are intratumoral developing T cells and are not TILs. Indications of immunotherapy for thymomas might be carefully considered, at least for type AB/B1/B2 thymomas.
Keywords: Thymoma; thymus; T cell development
Acknowledgments
Funding: None.
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://med.amegroups.com/article/view/10.21037/med-24-ab013/coif). The authors have no conflicts of interest to declare.
Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This study was approved by the Institutional Review Board of the Kyoto Prefectural University of Medicine (No. ERB-C-931) and informed consent was obtained from all individual participants.
Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.
doi: 10.21037/med-24-ab013
Cite this abstract as: Furuya T, Shimomura M, Okada S, Nakazono C, Uchibori A, Nishimura T, Kameyama K, Inoue M. AB013. Characteristic differences in the abundance of tumor-infiltrating lymphocytes and intratumoral developing T cells in thymoma. Mediastinum 2024;8:AB013.
