Cytokine Release Syndrome in HSCT May Affect Dendritic Cell Recovery and Early Development of aGVHD

Background: Cytokine release syndrome (CRS), also known as cytokine storm, is a severe systemic inflammatory response triggered by the activation of immune cells and the release of large quantities of cytokines and is characterized by fever and multi-organ dysfunction. With the spread of hematopoietic stem cell transplantation therapy, CRS is no longer limited to complications after chimeric antigen receptor T therapy. Acute graft-versus-host disease (aGVHD) represents a significant contributor to early mortality following allo-HSCT, exhibiting a notable morbidity. Dendritic cells (DCs) are non-redundant in regulating immunity and tolerance. Clinical and preclinical studies suggest that impaired reconstitution of donor DCs is associated with an increased risk of severe aGVHD. However, the relation of donor DCs with CRS is unknown. Methods: Fifty patients with acute leukemias undergoing allo-HSCT at the Children's Hospital of Soochow University were eligible for this study. Peripheral blood samples were collected from the patients after allo-HSCT, and DC subsets were analyzed by flow cytometry. CRS was defined as a new fever of 38°C or higher within 5 days of HSCT based on the absence of any evidence of infection. Univariate and multivariate logistic regression analyses were utilized to investigate the association between cytokine release syndrome (CRS), pDC reconstitution levels, and the occurrence of aGVHD. Mediation analysis was performed to explore the interrelationships between CRS, pDC reconstitution levels, and aGVHD. Results: The study cohort included acute myeloid leukemia (AML) (n=16, 32%), acute lymphoblastic leukemia (ALL) (n=32, 64%), and mixed phenotype acute leukemia (MPAL) (n=2, 4%). 49 graft source were PB /BM and 1 graft source was UCB. 36 graft types were HID, 11 were MURD , 3 were MRD and 1 was UCB. In the study, CRS occurred in 29 children, 48% on the day of transplantation and 38% on the first day after transplantation, with a median fever peak of 39.0°C (38.0, 40.4°C). 22 of the 29 children who developed CRS developed aGVHD within one month. Patients developing CRS after HSCT were found to have a lower frequency and several pDCs (median frequency, 0.01%; range, 0.00~0.06%, median number, 0.13cell/μl, range, 0.03~0.29 cell/μl) than patients without CRS (median frequency, 0.10%, range, 0.04%~0.17%, P=0.003; mediate number, 0.34 cell/μl, range, 0.18~0.62cell /μl, P=0.05). Patients who developed CRS showed significantly lower frequency CD1c+DCs (median, 0.02%; range, 0.01%~0.13%) than patients without CRS (median frequency, 0.15%; range, 0.03%~0.26%, P=0.017). The occurrence of CRS (Odd ratio [OR] = 10.06 [95%CI 2.89-41.15], p < 0.001) and pDC reconstitution levels (OR = 0.23 [95%CI 0.08-0.49], p < 0.001) were found to be associated with aGVHD, which occurred during the first month after transplantation. Based on mediation analysis, with pDC reconstitution level as the mediator, we found that the total effect of CRS on aGVHD was 0.52 (0.26 ~ 0.73, p < 0.001 ), the average direct effect (ADE) of CRS on aGVHD was 0.37 (0.079 ~ 0.64, p < 0.001), and the average causal mediation effect (ACME) of pDCs was 0.14 (0.06 ~ 0.29, p < 0.001 ). These data suggest that the CRS is linked to the occurrence of aGVHD, especially during the first month after HSCT, and this may be achieved by influencing the immune reconstitution of pDCs. Conclusion: CRS was associated with the level of pDC reconstruction and the development of aGVHD within one month after HSCT. CRS promotes the occurrence of aGVHD, whereas pDC reconstruction level is a protective factor. It would be beneficial to investigate the mechanisms by which CRS affects the immune reconstitution of DCs, particularly pDCs, in the initial stages of HSCT and subsequently influences the development of aGVHD. This could potentially lead to the control of the initial trigger for aGVHD.