Reactivation of occult hepatitis B virus infection, following treatment of refractory rheumatoid arthritis with abatacept

To the Editor: with many apoptotic and ballooned hepatocytes (Fig. 1A). Moderate steatosis was also present. Portal inflammatory cell infiltration was mild. Immunohistochemical stain for HBcAg showed extensive nuclear and cytoplasmic expression in hepatocytes, indicative of active viral replication (Fig. 1B). Immunohistochemical stain for HBsAg was negative. The basic medical treatments and laboratory data pertaining to HBV infection over time are depicted in Fig. 2. Abatacept is a soluble fusion protein which links the cytotoxic T-lymphocyte antigen-4 (CTLA-4) extracellular domain to the Fc region of the IgG molecule. CTLA-4 is an inhibitory T cell receptor, similar to CD28 in structure, expressed by activated and regulatory T cells (Tregs). CTLA-4 is constitutively expressed on CD4 CD25 Tregs, and such expression is important for Treg-mediated