ICOS and autoimmune thrombocytopenic purpura: Moreover, BM CD4+CXCR5+ Tfh and CD4+CXCR5+ICOS+ Tfh percentages were significantly higher than their PB counterparts in ITP group (CD4+CXCR5+: 21.43 ± 3.94 % % vs. 17.01 ± 4.47 %, P = 0.016; CD4+CXCR5+ICOS+: 5.42 ± 2.56 % vs. 3.21 ± 1.75 %, P = 0.018; Figure 5I and J).