Alloimmunization to transfused HOD red blood cells is not increased in mice with sickle cell disease

Abstract

Background Increased rates of RBC alloimmunization in patients with sickle cell disease may be due to transfusion frequency, genetic predisposition, or immune dysregulation. To test the hypothesis that sickle cell pathophysiology influences RBC alloimmunization, we utilized two transgenic mouse models of sickle cell disease. Study Design and Methods Transgenic sickle mice, which express human α and βS globin, were transfused with fresh or 14-day stored RBCs containing the HOD (hen egg lysozyme, ovalbumin, and human Duffyb) antigen; some recipients were inflamed with poly (I:C) prior to transfusion. Anti-HOD alloantibody responses were subsequently measured by ELISA and flow crossmatch; a cohort of recipients had post-transfusion serum cytokines measured by bead array. Results Both Berkeley and Townes homozygous (SS) and heterozygous (AS) mice had similar rates and magnitude of anti-HOD RBC alloimmunization following fresh HOD RBC transfusion compared with control animals; under no tested condition did homozygous SS recipients make higher levels of alloantibodies than control animals. Unexpectedly, homozygous SS recipients had blunted cytokine responses and lower levels of anti-HOD alloantibodies following transfusion of 14-day stored RBCs, compared with control animals. Conclusions In sum, homozygous βS expression and the ensuing disease state are not alone sufficient to enhance RBC alloimmunization to transfused HOD RBCs in 2 distinct humanized murine models of sickle cell disease under the conditions examined. These data suggest other factors may contribute to the high rates of RBC alloimmunization observed in humans with sickle cell disease.

Red blood cell alloimmunization in sickle cell disease: pathophysiology, risk factors, and transfusion management

“…Hendrickson et al reported that sickle mice (Berkeley and Townes), with or without pretreatment with a viral-like inflammatory stimulus, have a similar rate of alloimmunization compared with wild-type animals, concluding that perhaps expression of other modifying genes besides HbS may be responsible for enhanced RBC alloimmunization in SCD. 52 Extrapolating these data to humans must be done with caution, however, because there are inherent differences between clinical features of human SCD and available mouse models, 53 and only one example of alloimmunization (to HOD antigen) after a single transfusion was studied. 52 It is currently unknown whether alloimmunization rates differ depending on the presence or absence of clinical complications of SCD.…”

“…52 Extrapolating these data to humans must be done with caution, however, because there are inherent differences between clinical features of human SCD and available mouse models, 53 and only one example of alloimmunization (to HOD antigen) after a single transfusion was studied. 52 It is currently unknown whether alloimmunization rates differ depending on the presence or absence of clinical complications of SCD. For example, it remains unclear whether patients during acute vaso-occlusive crisis (VOC) have an altered alloimmunization potential.…”

“…74,82 Incubation of stored donor RBCs in the pretransfusion plasma from SCD patients encountering DHTR without detectable antibodies caused the stored RBCs to undergo eryptosis, 80 an antibody-independent phenomenon characterized by erythrocyte shrinkage, membrane blebbing, and PS exposure, all classic features of apoptotic death of nucleated cells and observed in aging or damaged erythrocytes. 83 52 suggesting a role for FY protein in hyperhemolytic reactions without detectable antibodies.…”

Factors Influencing RBC Alloimmunization: Lessons Learned from Murine Models

“…To investigate the impact of the sickle β-globin gene in a reductionist model, transgenic animals with sickle cell disease were transfused with transgenic RBCs expressing the HOD antigen, and alloimmune responses were measured longitudinally [92]. Animals with sickle cell disease (including Berkeley and Townes animals, which express the human sickle β-globin gene) had similar responses to transfused HOD RBCs as did littermate controls with sickle cell trait or hemoglobin AA.…”

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

“…However, it has been shown that SCD does not increase the rate of alloimmunization in mice. 10 Despite important differences in the immune system between mice and humans, mouse models enable the investigation of different parameters separately, and provide hypotheses that can be tested in humans. Murine models of post-transfusion alloimmunization have been developed, such as those expressing transgenic human antigens, e.g.…”