ATTACHMENT OF CHRONIC LYMPHOCYTIC LEUKAEMIA CELLS BY AUTOLOGOUS POLYMORPHONUCLEAR NEUTROPHILS MEDIATED BY BISPECIFIC...

Chronic lymphocytic leukemia (CLL) is the most common adult leukaemia in the US and in Europe, including Georgia. CLL presents with clonal expansion and accumulation of CD5+CD19+CD23+ cells in peripheral lymphoid organs and tissues and in bone marrow. The disease remains incurable, albeit there are new molecular and immunotherapy methods currently available, which, in conjunction with chemotherapy, lead to the "precision therapy" approach. The majority of immunotherapies are based on the ability of therapeutic antibodies to mobilize anti-tumour potential of immune responses. Bispecific antibodies (BsAb) are also considered in the treatment of CLL, whereby phagocytic cells play a key effector role in the destruction of the target CLL cells. Anti-CD19/anti-CD64 BsAb binds to CD19 receptors on CLL cells and to CD64 receptors (FcγRI) on monocytes and activated polymorphonuclear neutrophils (PMNs), thus inducing phagocytosis of the leukaemic cells. The aim of this study was to evaluate the ability of anti-CD19/CD64 BsAb to enhance adherence of CLL cells by PMNs, intact or activated with G-CSF and IFNγ cytokines. Membranes of the isolated CLL cells of 16 patients were stained with Red Fluoresent Linker and CLL cells were co-incubated with isolated autologous PMNs, intact or pre-stimulated with G-CSF and/or IFNγ for 4h or 24h. The PMN/CLL cell adhesion was analyzed with the FACScan flow cytometer by gating on PMNs with adhered RFL-stained CLL cells. The results were heterogenous. Our data demonstrate that anti-CD19/anti-CD64 BsAb has limited capacity to enhance leukemic cell attachment by autologous PMNs. This could partially be explained by the remarkable intensity of spontaneous ability of PMNs to adhere to autologous CLL cells. Pre-treatment of PMNs from CLL patients with G-CSF and INFγ, alone or jointly did not enhance the adhesion of the leukaemic cells. Moreover, G-CSF and IFNγ joint effect led to the reduction in the adhesion capacity of the effector PMNs. It appears, that therapeutic effect of anti-CD19/anti-CD64 BsAb on enhancing attachment of leukaemic cells to PMNs in CLL patients is limited and its application should be based on the assessment of individual capacity of the patients' phagocytic cells.