Rituximab Reduces the Incidence of Acute Graft Versus Host Disease and Delays CD3+CD4+ Lymphocyte Recovery.

The monoclonal antibody Rituximab has been successfully used to treat steroidrefractory chronic graft versus host disease (cGvH) after allogeneic stem cell transplantation (SCT). We hypothesized that Rituximab might reduce the incidence of aGvH. We found that patients conditioned with a regimen containing Rituximab experienced significantly less aGvH when compared to a regimen without Rituximab (23.1% versus 66.7%, p = 0.032). Furthermore did we find that the recovery of CD3+CD4+ lymphocytes was delayed following administration of Rituximab. As expected, patients were devoid of CD19+CD20+ B lymphocytes after administration of Rituximab; interestingly, both the recovery of CD3+CD8+ lymphocytes and CD16+CD56+ NK cells did not differ between patients receiving Rituximab and Rituximab-naíve patients. Furthermore, our data revealed a significant correlation of the transplants CD34+ HSC content with the occurrence of aGvH (p = 0.031) but only a trend towards a correlation of CD3+ cells with the occurrence of aGvH (p = 0.274). Taken together, our data establish a mechanism of how Rituximab might reduce the incidence of aGvH next to depleting host and perhaps donor antigen presenting cells. It remains to be elucidated whether this effect translates to a graft versus tumor effect and to survival as well.