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Thank you for attending THSNA 2026. The virtual meeting is now closed.
Thank you for attending THSNA 2026. The virtual meeting is now closed.
Presentation Details
| Innate Immune Cell Activation is Associated with Anaphylactic Outcomes in Factor IX Exposed Hemophilia B Mice Huong Chau, Elizabeth York, Athena S Aragon, Veronica Gonzalez-Pena, Charles Gawad, Glaivy Batsuli. Stanford University, Palo Alto, CA, USA |
Abstract
Background: Development of antibodies against coagulation factor IX (FIX) is a rare treatment complication in hemophilia B, but is uniquely associated with the onset of hypersensitivity reactions and anaphylaxis. Dendritic cells (DC) are crucial players in the innate and adaptive immune response to antigens. Specifically, type 2 conventional DC (cDC2) has been described as the key mediator of T follicular helper cells and germinal center responses. Whether cDC2 or other antigen presenting cell (APC) subsets contribute to the anaphylactic response observed in FIX immunity has yet to be investigated. Objective: To investigate splenic DC subset dynamics and signaling pathways in the early immune response to FIX in two distinct hemophilia B mouse models. Methods: C3H/HeJ FIX knockout (KO, anaphylactic model) and C57BL/6 FIX KO mice (non-anaphylactic model) at 8–12 weeks old (n =8-10) received weekly injections of recombinant FIX for 3 or 6 weeks or normal saline (NS) for 6 weeks as a control. Platelet-activating factor (PAF) antagonist and anti-histamine triprolidine was necessary in C3H/HeJ FIX KO mice to enable >3 weeks of FIX injections. Anti-FIX IgG levels were measured by ELISA. Splenic APC subsets were assessed by flow cytometry and single-cell RNA sequencing (scRNAseq). DC subsets evaluated consisted of type 1 conventional DC (cDC1), cDC2, plasmacytoid DCs (pDCs), and monocyte-derived DCs (MoDCs). Results: In C3H/HeJ FIX KO mice, administration of PAF antagonist with an anti-histamine suppressed anaphylaxis-associated death but did not alter anti-FIX IgG antibody formation. C3H/HeJ FIX KO mice injected with 3 vs. 6 weekly FIX doses had median anti-FIX IgG1 titers of 8 ng/ml and 1301 ng/ml, respectively. C57BL/6 FIX KO injected with FIX or NS had median anti-FIX IgG1 titers of 0 ng/ml. C3H/HeJ FIX KO that received 3 FIX injections and developed anaphylaxis had a significant increase in cDC2 frequency by 30% and 36% decrease in cDC1 frequency compared to C3H/HeJ FIX KO mice with suppressed anaphylaxis that developed anti-FIX antibodies after 6 FIX injections and NS-injected C3H/HeJ FIX KO mice. Interestingly, the 3-injection C3H/HeJ FIX KO cohort had a higher abundance of macrophages compared to all other injection cohorts. The anaphylactic C3H/HeJ FIX KO 3-injection FIX cohort showed significant enrichment of pathways related to regulation of the inflammatory response (P = 0.029), chronic inflammatory response (P = 0.028), and activation of the innate immune response (P = 0.026) within the combined DC subset compared to the C3H/HeJ FIX KO 6-injection FIX cohort. Notably, the proinflammatory MoDCs in C3H/HeJ FIX KO mice that received 6 FIX injections demonstrated significant upregulation in complement and type 1 interferon pathways. Conclusion: Immunophenotyping and transcriptomic analysis of hemophilia B mice prone to anaphylaxis and antibody development with FIX exposure reveal an associated with innate immune cell activation, particularly in the cDC2 subset, and a proinflammatory gene signature. Additional studies are planned to further assess and validate the transcriptomic signature across all APC subsets to identify distinguishing markers between the anaphylaxis vs. non-anaphylactic models.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.