Absence of response to rituximab in patients with refractory primary immune thrombocytopenia

Abstract

To explore the possible causes for an absence of response to rituximab (RTX) in patients with refractory immune thrombocytopenia (ITP). A total of 20 refractory ITP patients on RTX therapy and 10 health volunteers were recruited from 2008 to 2013. Memory T lymphocytes (Tm) (CD4(+)CD45RO(+)) and B lymphocytes (CD19(+)CD20(+)) in peripheral blood (PB) were examined by flow cytometry (FCM). And enzyme-linked immunosorbent assay (ELISA) was employed for detecting the platelet-associated antibodies IgG/IgM (PAIgG/IgM). (1) 12 patients with refractory ITP achieved a good response after therapy with RTX (effective RTX group) and 8 cases failed to respond (ineffective RTX group). The PB levels of CD4(+)CD45RO(+)Tm were 41.33% ± 9.62% and 45.36% ± 8.57% respectively at pre-therapy and post-therapy in ineffective RTX group. And significant differences existed between ineffective and effective RTX groups (22.36% ± 11.57%, 26.65% ± 6.32%) versus health volunteers (19.72% ± 7.35%, 20.64% ± 7.35%) (all P < 0.05) . No statistical differences existed in the PB level of CD4(+)CD45RO(+)Tm between pre-therapy and post-therapy in ineffective or effective RTX group (both P > 0.05); (2) The PB level of CD19(+)CD20(+)B lymphocytes in RTX ineffective group was lower than that at pre-therapy in RTX effective group (16.36% (6.17%-27.53%) vs 45.72% (35.80%-57.19%), P < 0.05) . No significant difference existed in the level of CD19(+)CD20(+)B at post-therapy between ineffective and effective RTX groups (6.67% (4.09%-19.17%) vs 5.19% (3.78%-17.39%), P > 0.05). And significant differences existed in the PB level of CD19(+)CD20(+)B between pre-therapy and post-therapy in ineffective or effective RTX group (both P > 0.05); (3) PAIgG/IgM was not detected in RTX ineffective group. And PAIgG/IgM was found in 11 cases at pre-therapy versus 1 case at post-therapy in RTX effective group. CD4(+)CD45RO(+)Tm is probably associated with an absence of response to RTX in patients with refractory ITP.