Eosinophils are not required for the induction and maintenance of an alloantibody response

Eosinophil-produced cytokines have been shown to participate in the maintenance of antigen-specific plasma cells (PC) in bone marrow (BM), suggesting that eosinophils are required in the development and/or maintenance of alloantibody responses posttransplant. To test this hypothesis, we sensitized eosinophil-deficient ΔdblGATA1 mice and wild-type (WT) control mice with allogeneic splenocytes or with allogeneic heart grafts and compared the kinetics and titers of serum donor-specific antibodies (DSA), as well as BM and spleen CD130 + B220 low PC populations between groups. Spleen cells from naïve ΔdblGATA1 BALB/c mice contained higher percentages of PC than WT without detectable differences in BM PCs. After sensitization with allogeneic splenocytes, BALB/c ΔdblGATA1 mice contained fewer BM PCs but more splenic PCs compared to controls. These differences were associated with modestly lower titers of serum DSA 4 and 12 weeks after sensitization but secondary immunizations induced similar increases in both groups. Moreover, the kinetics and strength of DSA did not differ in WT and ΔdblGATA1 BALB/c mice transplanted with B6 cardiac allografts, nor did they differ in transplanted ΔdblGATA1 and WT mice on a B6 background. Therefore, eosinophils are not required for alloantibody formation or maintenance in mice and are thus unlikely to be effective targets for antibody desensitization. In contrast to a previously reported requirement for eosinophils in the maintenance of plasma cells reactive to nominal antigens, this transplant study performed in eosinophil-deficient mice unexpectedly indicates that eosinophils are not required for the induction and/or maintenance of donor reactive alloantibodies. See editorial by Kers and Florquin on page 2522.