Prevalence of proliferating CD8⁺ cells in normal lymphatic tissues, inflammation and cancer

Area of Science:

• Immunology
• Oncology
• Pathology

Background:

• CD8+ cytotoxic T-lymphocytes are crucial for anti-tumor immunity.
• Understanding T-cell expansion is key to cancer immunology.
• Ki67 is a marker of cellular proliferation.

Purpose of the Study:

• To quantify the percentage of proliferating CD8+ T-cells (Ki67+CD8+) in various tissue types.
• To investigate the role of Ki67+CD8+ cells in normal lymphoid tissues, inflammatory diseases, and cancers.
• To explore the association of Ki67+CD8+ cells with clinicopathological features in colorectal cancer.

Main Methods:

• Multiplex fluorescence immunohistochemistry was employed.
• Analysis was performed on large tissue sections and tissue microarrays (TMAs).
• Over 20 compartments of normal lymphoid tissues were evaluated, alongside inflammatory diseases and 765 colorectal cancer samples.

Main Results:

• In normal lymphoid tissues, proliferating CD8+ T-cells (Ki67+CD8+) generally did not exceed 3%.
• Inflammatory diseases showed more variable and higher percentages of Ki67+CD8+ cells compared to normal tissues.
• In colorectal cancers, Ki67+CD8+ cells were more abundant in the tumor center than at the invasive margin and significantly associated with microsatellite instability, pT, and pN categories.

Conclusions:

• The baseline proliferation rate of Ki67+CD8+ cells in healthy lymphoid organs is typically below 3%.
• This proliferation rate is significantly elevated in inflammatory and neoplastic diseases.
• The strong correlation with unfavorable tumor features in colorectal cancer suggests Ki67+CD8+ cell assessment may predict patient outcomes.