Anti-CD20 Antibody Prevents Red Blood Cell Alloimmunization in a Mouse Model.

Alloimmunization against RBCs can cause life-threatening delayed hemolytic transfusion reactions. Anti-CD20 Ab has recently been used to prevent alloimmunization. However, its effects remain unclear, particularly in lymphoid organs. We investigated the impact of murine anti-CD20 Ab in the blood and spleen. We assessed protocols for preventing primary alloimmunization and for abolishing established alloimmunization. Prophylactic protocols prevented alloimmunization. However, anti-CD20 treatment could only limit the further amplification of established alloimmunization. Residual B cell subtype distribution was disrupted in the spleen, but adoptive transfer studies indicated that these cells were neither plasma nor memory cells. Anti-CD20 Ab had a major effect on alloreactive CD4+ T cells, increasing the expansion of this population and its CD40 expression, while lowering its CD134 expression, thereby confirming its role in alloimmunization. In conclusion, this study shows that anti-CD20 immunotherapy can prevent RBC Ab development. However, this immunotherapy is limited by the increase in alloreactive CD4+ T lymphocytes. Nevertheless, treatment with anti-CD20 Abs should be considered for patients requiring transfusion with a very high risk of alloimmunization and life-threatening complications.

Red blood cell alloimmunization is influenced by the delay between Toll-like receptor agonist injection and transfusion.

Murine models of red blood cell transfusion show that inflammation associated with viruses or methylated DNA promotes red blood cell alloimmunization. In vaccination studies, the intensity of antigen-specific responses depends on the delay between antigen and adjuvant administration, with a short delay limiting immune responses. In mouse models of alloimmunization, the delay between the injection of Toll-like receptor agonists and transfusion is usually short. In this study, we hypothesized that the timing of Toll-like receptor 3 agonist administration affects red blood cell alloimmunization. Poly(I:C), a Toll-like receptor 3 agonist, was administered to B10BR mice at various time points before the transfusion of HEL-expressing red blood cells. For each time point, we measured the activation of splenic HEL-presenting dendritic cells, HEL-specific CD4(+) T cells and anti-HEL antibodies in serum. The phenotype of activated immune cells depended on the delay between transfusion and Toll-like receptor-dependent inflammation. The production of anti-HEL antibodies was highest when transfusion occurred 7 days after agonist injection. The proportion of HEL-presenting CD8α(+) dendritic cells producing interleukin-12 was highest in mice injected with poly(I:C) 3 days before transfusion. Although the number of early-induced HEL-specific CD4(+) T cells was similar between groups, a high proportion of these cells expressed CD134, CD40 and CD44 in mice injected with poly(I:C) 7 days before transfusion. This study clearly shows that the delay between transfusion and Toll-like receptor-induced inflammation influences the immune response to transfused red blood cells.