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

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.