Plasmablasts are particularly affected by leflunomide and teriflunomide.126,127 Teriflunomide exhibits a similar effect in patients with MS compared to patients with rheumatoid arthritis on leflunomide, whereby the percentage of circulating memory B cells does not change.127,128 However, in some instances, the absolute number of CD19+ B cells decreases, significantly reducing circulating memory B-cell numbers.128,129 In addition, leflunomide and teriflunomide have pan-antiviral activity and may work in MS by inhibiting lytic EBV infection.130-133. Here, CD19 is linked to rheumatoid arthritis.