Regulatory T lymphocytes in regional lymph nodes of patients with colorectal cancer

Objective: to identify changes in the regulatory T cell (Treg) pool and the expression level of inducible T-cell costimulator (ICOS) and programmed cell death protein (PD-1) on their membrane in metastatic lymph nodes in colorectal cancer (CC). Material and methods. The main group consisted of 105 patients with stage III CC. The clinical comparison group consisted of non-neoplastic pathology (developmental anomalies, stomas, diverticular disease of the colon). The Treg pool and the expression of PD-1 and ICOS were studied using flow cytometry. Results. In metastatic lymph nodes with RTC, the content of Treg increases by 3.5 times (p<0.001), the relative number of naive Treg decreases (p<0.001), the number of central memory Treg expressing CD197 on their membrane increases almost 2 times (p<0.001), and effector memory cells with the CD45RA–CD197– phenotype increase 3.6 times (p<0.001). The number of PD-1−ICOS+ Treg in the total population of CD3+ lymphocytes increases by 3.1 times (p<0.001). The number of Treg with the CD19−CD3+CD4+CD25highCD127−PD-1+ICOS+ phenotype increases by 1.5 times (p<0.001) compared to the control. Conclusion. In patients with RTC, the number of naive Treg in metastatically affected lymph nodes decreases, the relative content of central and effector memory Treg increases, the number of Treg expressing ICOS increases, as well as those simultaneously expressing both the inhibitory protein PD-1 and the stimulating molecule ICOS.