IFNB1 and myeloid sarcoma: For instance, when PBMCs were taken from 23 MS patients treated with IFNβ, and T cell proliferation was measured following IFNβ incubation, the T cells demonstrating the highest response rate came from patients that had developed ADA.53 Furthermore, in two MS patients that were positive for anti-natalizumab antibodies also had natalizumab reactive T cells.4