Expression of immune checkpoint markers in peripheral blood lymphocytes of women with fibroadenoma of the breast

Abstract

Changes of the immune state in patients with fibroadenoma (FA) or other benign lesions of the breast, as well as the involvement of immune checkpoints in pathogenesis of these lesions, remain underexplored. The aim of this study was to compare the expression level of the key immune checkpoint markers CD279/PD-1, CD274/PD-L1, CD366/TIM3, and CD223/LAG3 in total circulating lymphocytes, T cell population as well as in its CD4 and CD8 subsets in peripheral blood from women with breast FA and healthy controls. Blood samples were taken from 12 women diagnosed with FA of the breast (aged 23-54 years, FA group) and 15 healthy women (aged 22-52 years, control group). Sample uptake was performed immediately before surgery, and samples were further analyzed by multicolor flow cytometry using monoclonal antibodies CD3-VioBlue, CD4/CD8-FITC, PD1-PE, PD-L1-PerCP-Cy.5.5, and TIM3/LAG3-APC. Each sample was incubated with 4 antibody combinations: CD3/CD4/PD1/PD-L1/TIM3, CD3/CD4/PD1/PD-L1/LAG3, CD3/CD8/PD1/PD-L1/TIM3, and CD3/CD8/PD1/PD-L1/LAG3. First, mono-expression of each of the 4 immune checkpoint markers was evaluated in the lymphocyte gate from both investigated groups. In FA samples, a significant increase in PD-L1 expression (assessed as percent of positive cells and fluorescence intensity change) was observed. Regarding expression of immune checkpoints in CD3+ T cells, along with significantly increased %PD-L1+, elevated numbers of PD1+T cells were detected. As for the differences in immune checkpoint expression changes between CD4+ and CD8+ T cell subsets, FA patient group demonstrated a more prominent increase in the amount of CD8+PD1+T cells relative to CD4 subset. The profiles of PD-L1 changes in CD4 and CD8 subpopulations were comparable showing, in both cases, a significant increase in FA sample group. We also analyzed changes in co-expression of any two immune checkpoint markers in CD4+ and CD8+ T cell subsets. The most noticeable was as increase in the prevalence of PD1+PD-L1+ phenotype in both T cell subpopulations from FA patients compared to the controls. With respect to co-expression of 3 checkpoint markers in CD4+ and CD8+ T cells, a significant increase in the percentage of PD1+PD-L1+TIM3+ cells among CD4 T helpers was found in FA. Thus, specific changes of T cell phenotype related to (co-)expression of immune checkpoint regulators may occur in systemic circulation of women with breast FA.

Keywords

• fibroadenoma of the breast
• immune checkpoints
• peripheral blood lymphocytes
• flow cytometry
• co-expression
• immune regulation