EXPRESSION FEATURES OF ANTIGENS INVOLVED IN THE FORMATION OF IMMUNOLOGICAL SYNAPSE IN CHRONIC LYMPHOCYTIC LEUKEMIA

Abstract

Background. Chronic lymphocytic leukemia (CLL) is a lymphoproliferative disease that manifests by the accumulation of tumor monoclonal B-lymphocytes in the bone marrow, peripheral blood and secondary lymphoid organs. Recently it was found that CLL cells are able to form immunological synapses with microenvironment cells, directly and indirectly affecting their function. Therefore, it became clear that the pathogenesis of CLL is not only escape of apoptosis but also the ability of CLL cells to cause T-lymphocyte anergy, thereby avoiding immune surveillance. Objective: to study the expression of FAS, co-stimulatory molecules CD80 and CD86, PD-1, PD-L1 on CLL cells, and also to study the basic subpopulations of T-cells (naїve, memory, effector cells). Materials and methods. The study included 46 CLL patients: 16 patients with disease progression after chemotherapy and 30 patients with newly diagnosed CLL. “Primary” patients are categorized according to J. Binet’s CLL stages. Stage A was established in 14 patients, B – 10, C – 6. The control group included 29 healthy donors. Peripheral blood was used as a material for analysis. The study was performed on a 6-color flow cytometer BD FACS Canto II (BD Biosciences, USA). Results. In CLL patients, the proportion of CD80+, CD86+, FAS+ B-cells was significantly lower than in donors. In “primary” patients the proportion of CD80 + CLL cells was higher than in patients with CLL progression. Among “primary” patients the proportion of CD80+ and CD86+ was lower in advanced stages of the disease. In patients with CLL progression the proportion of FAS+ B cells was higher than in “primary” patients. The proportion of PD-1+ B cells in CLL patients was higher than in donors and “primary” patients. The proportion of PD-1+ tumor cells was significantly lower in advanced stages of the disease. The proportion of PD-L1+ B cells in CLL patients was lower than in donors. Among the “primary” patients, the proportion of PD-L1+ B-lymphocytes was higher in stage A. The proportion of PD-1+ Thelpers was higher in CLL patients than in donors, and among “primary” patients it was higher in advanced stages of the disease. The proportion of PDL1+ T-helpers and cytotoxic T-cells in CLL patients was lower than in donors. The proportion of naїve cells (CD95-CD28+) in patients compared with donors was lower and the proportion of effector cells (CD95+ CD28–), memory cells (CD95 + CD28 +) was higher, a proportion of CD8+ memory T-cells was higher among patients in the advanced stage of CLL. Conclusion . Therefore, a decline the CD80/CD86+ B-cells in CLL can cause ineffectiveness of an immunological synapse between tumor cells and T-cells, which leads to anergy of T-lymphocytes. Decline expression of the FAS receptor allows tumor CLL cells to avoid FAS-mediated apoptosis. A change in the T-cell pool toward memory cells and effectors, the acquisition of a CD4+PD-1+ (“exhausted”) phenotype impaired antitumor immunity and possible leads to disease progression.