Rituximab-induced direct inhibition of T-cell activation.

BACKGROUND: Rituximab, an anti-CD20 monoclonal antibody, is reported to increase the T-cell-dependent infection risk. The current study was designed to investigate whether rituximab interferes with T-cell activation. PATIENTS AND METHODS: Patients with non-Hodgkin lymphoma receiving 4-6 courses of 375 mg/m(2) rituximab underwent detailed assessment of T-cell activation pre- and post-rituximab. A similar analysis assessed the in vitro effect of rituximab on T-cell activation in response to allogeneic dendritic cells (allo-DCs) and other stimuli.
RESULTS: Patients receiving rituximab exhibited a significant decline in IL-2 and IFN-γ levels in peripheral blood, most prominent after repeated rituximab courses. Evaluation at 3 months after rituximab therapy showed restoration of inflammatory cytokine production. Similarly, in vitro stimulation of peripheral blood mononuclear cells in the presence of rituximab resulted in a significant decrease in T-cell activation markers, inflammatory cytokine production and proliferative capacity. These effects were also observed using B-cell-depleted T cells (CD3(+)CD25(-)CD19(-)) and were accompanied with disappearance of CD3(+)CD20(dim) T-cell population.
CONCLUSION: Rituximab administration results in transient, dose-dependent T-cell inactivation. This effect is obtained even in B-cell absence and may increase the infection risk.