Shifts in subpopulations and immunophenotypic subsets of normal blood lymphocytes in the patients with chronic lymphocytic leukemia during immunochemotherapy

Immunological changes in normal lymphocytes subpopulations in blood of patients with chronic lymphocytic leukemia (CLL) may play a negative role in the disease progression. The aim of our study was to evaluate the effect of immunochemotherapy on the subpopulation composition and immunophenotypic features of normal lymphocytes in blood of CLL patients. Patients and methods: The study included 37 men, 25 women with CLL at Binet stages B, C, median age 64 (50-71) years old. The patients received 6 cycles of immunochemotherapy: RB (Rituximab + Bendamustine), or FCR (Fludarabine + Cyclophosphamide + Rituximab). The subpopulation profile of polyclonal B cells, T lymphocytes (T helpers, T-regulatory cells, T cytotoxic cells), NK lymphocytes, as well as expression of PD1, PD-L1, LAG3 were studied in blood samples of patients before and after treatment. The studies were performed using flow cytometry technique (Navios 10/3, Beckman Coulter, USA). Statistical analysis is performed in Statistica 13.0. Results: The study showed that all patients with CLL had significant quantitative and functional changes in the subpopulation profiles of B, T, and NK lymphocytes before and after therapy. The proportion of normal polyclonal B cells among all lymphocytes before treatment was reduced being characterized by PD1 expression. The therapy leads to partial restoration of the normal B cell population, which did not show expression of PD1, PD-L1, LAG3. Before and after treatment, CD4+ and CD8+T cells showed the highest expression of PD1, thus suggesting alterations of their antitumor functions. After treatment, the T lymphocyte microenvironment tends to recover due to an increase in their number. However, persistence of PD1 expression on T cells apparently prevents the complete restoration of their functional activity. Moreover, an increased content of T-regulatory cells, and maintenance of PD1 and LAG3 expression on NK lymphocytes may promote suppression of antitumor immune response and reduce the probability of long-term remission. In this regard, monitoring of immunological parameters during therapy is useful for assessing the degree of immune response dysregulation and, thus, timely planning of antitumor treatment and corrective immunotherapy.