The clinical course of chronic lymphocytic leukemia is often insidious, but it is a disease that remains not treatable. Even using the best therapeutic options, symptomatic patients have a survival between 1-7 years. Several series of therapeutic combinations have been evaluated for patients with relapses and refractory to treatment, but none has been demonstrated to be superior. Therefore, it is notable the need to find therapeutic alternatives for these patients. Different studies in phase II have shown that the addition of rituximab to chemotherapy has improved the percentage of response and the disease free period. However, all patients suffer progression of the disease at long term. One of the main mechanisms of action of rituximab is the antibody mediated cytotoxicity. The most important effector cells involved in this mechanism of action are Fcγ receptors cells, specifically NK cells. The general hypothesis is the analysis of molecules enhancing the cytotoxic capacity of NK cells and ADCC, for them to be used in addition to rituximab as adjuvant in the treatment of chronic lymphocytic leukemia. Amongst these molecules, CpG ODN A was studied because its capacity to mimetise the stimulating activity of bacterial DNA through TLR9 and to induce a strong activation and synthesis of IFNγ by NK cells. The other molecule was IL-15, due to its involvement in survival, proliferation and activation of NK cells. It was observed that IL-15 and CpG ODN A were two stimulating molecules than significantly enhanced the cytotoxic capacity of PBMCs, in the presence or absence of rituximab, when they were confronted to cells from B lymphoma Raji line and to leukemic cells from CLL-B. The major effector population responsible for this cytotoxic enhancement are the NK cells. However, the mechanism of action is different. Whereas IL-15 increased the cytotoxic capacity of the NK cell directly as much as indirectly, CpG ODN A did it only indirectly, requiring of additional signals present in PBMCs. When PBMCs were confronted to Raji cells from B cell lymphoma, the two stimuli had a similar behavior. However, when PBMCs were confronted to leukemic cells from CLL-B, Il-15 was a stronger stimulus than CpG ODN A, enhancing the natural cytotoxicity and ADCC. In this way, IL-15 worked increasing the expression of receptors related to degranulating NK cells (CD16, CD69 and NKG2D) and of LFA-1 receptor, implied in the cytotoxicity signaling (cellular adhesion), and increasing significantly IFNγ production. In the presence of TGF-β, immunosupressor cytokine that decrease significantly the natural cytotoxicity and ADCC of PBMCs confronted to leukemic cells from CLL, IL-15 is able to counteract this suppressive effect. In the same way, the reduction caused in IFN-γ production is going to be smaller and more variable in the presence of IL-15, although not significantly.
Potenciació de la citotoxicitat cel·lular induïda pel Rituximab en cèl·lules B de LLC
Moga Naranjo, E. (Author). 6 Nov 2008
Student thesis: Doctoral thesis
Student thesis: Doctoral thesis