Relationship between NK Cell Activation and Clinical Response in Rheumatoid Arthritis Treated with Rituximab

We investigated the relationship between the anti CD20 therapy and the NK cell phenotype in patients with Rheumatoid Arthritis (RA).

patients with seropositive RA according to the ACR criteria that was refractory to conventional and anti TNF alpha agents were studied. All patients were treated with Rituximab (1.0 g at days 1 and 15). At baseline and day 30 were collected: absolute counts of B cells (CD19+), total T cells (CD3+), helper (CD3+CD4+), cytotoxic (CD3+CD8+) and NK (CD16+CD56+). As NK activation marker was used CD54bright expression. Disease activity was primarily assessed using the the Clinical Disease Activity Index (CDAI); in addition, we calculated the Disease Activity Score 28-joint assessment (DAS28).

18 patients were enrolled (mean age ± SD 58.6 ± 2.8 years old). After the rituximab course, as expected CD19+ cells were not detectable, the cytotoxic lymphocytes and CD56+CD16+ cells downregulated (283 ± 34 and 85 ± 15 respectively), instead an up regulation of CD56+CD16+CD54bright was observed (187 ± 43). The dynamic of NK cells activation was significantly associated with clinical variables (r=0.811, p<0.001).

our data suggest a role of rituximab therapy in varying NK phenotype in patients with RA and show that NK cells activation correlates with clinical response.