B cell monitoring of transplant patients treated with anti-CD20.

B cell depletion with the monoclonal anti-CD20 antibody, rituximab, is being used increasingly in clinical transplantation. This chapter reviews the clinical uses and potential immunological consequences of rituximab therapy in the setting of solid organ transplantation. In clinical transplantation, therapy with rituximab is contemplated in cases of rejection that are refractory to conventional immunosuppression. B cell targeted therapy is also being used to lower the risk of allosensitization. The biological effects of rituximab are complex and include a reduction in de novo alloantibody production, shifts in circulating B cell subsets and repertoire, and effects on other immune system cells such as T cells. The chapter concludes with detailed recommendations for clinical laboratory monitoring of rituximab-treated transplant patients, particularly with respect to immunophenotyping of peripheral blood lymphocytes to assess the emergence of transitional B cells during B cell reconstitution. Careful monitoring of the immune system in rituximab-treated transplant patients may yield important insights into B lymphocyte biology and immune tolerance.