{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T05:40:52Z","timestamp":1777354852168,"version":"3.51.4"},"reference-count":46,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T00:00:00Z","timestamp":1777334400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:p>Insufficient immune reconstitution (IR) is a major determinant of morbidity and mortality after allogeneic hematopoietic cell transplantation (allo-HCT). Strategies for graft-versus-host disease (GVHD)-prophylaxis, such as anti-thymocyte globulin (ATG) and post-transplant cyclophosphamide (PTCy), modulate immune recovery, but their effects on IR in matched unrelated donor (MUD) allo-HCT remain incompletely defined. In this retrospective bi-centric study, we analyzed patients with myeloid malignancies undergoing MUD allo-HCT who received ATG or PTCy per center policy. Longitudinal IR and clinical outcomes were assessed. IR was defined as sustained recovery of CD3+CD4+ cells &amp;gt;200\/\u03bcl and CD19+ cells &amp;gt;50\/\u03bcl. The impact of GVHD-prophylaxis (ATG vs PTCy) on IR dynamics was explored. A total of 252 patients were included. By day +365, 16.7% achieved IR, which was independently associated with superior OS (HR 0.39, 95% CI 0.17\u20130.90; p=0.026) and lower TRM (HR 0.08, 95% CI 0.01\u20130.63; p=0.017). In multivariable competing-risk analyses, younger donor age (sHR 0.97, 95% CI 0.94\u20131.00; p=0.037) and PTCy (sHR 0.49, 95% CI 0.27\u20130.84; p=0.01) were associated with higher probability of IR by month +18. The association between PTCy and IR was attenuated after adjusting for therapy-requiring acute or chronic GVHD, which independently delayed IR (HR 0.31, 95% CI 0.20\u20130.48; p&amp;lt;0.001). ATG and PTCy showed distinct IR trajectories: ATG associated with earlier NK expansion, PTCy led to enhanced adaptive T- and B-cell recovery from day +100. IR strongly predicted survival, independently of GVHD-prophylaxis. Prospective studies are warranted to better define determinants of IR after MUD allo-HCT in the PTCy era.<\/jats:p>","DOI":"10.3389\/fimmu.2026.1820251","type":"journal-article","created":{"date-parts":[[2026,4,28]],"date-time":"2026-04-28T04:53:01Z","timestamp":1777351981000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Impact of post-transplant cyclophosphamide and anti-thymocyte globulin on immune reconstitution in MUD allo-HCT"],"prefix":"10.3389","volume":"17","author":[{"given":"Giulia","family":"Furnari","sequence":"first","affiliation":[{"name":"Universit\u00e0 Vita-Salute San Raffaele","place":["Milan, Italy"]},{"name":"Hematology and Bone Marrow Transplantation Unit, San Raffaele Scientific Institute IRCCS","place":["Milan, Italy"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Verena","family":"Wais","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine III, 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Italy"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Annalisa","family":"Ruggeri","sequence":"additional","affiliation":[{"name":"Hematology and Bone Marrow Transplantation Unit, San Raffaele Scientific Institute IRCCS","place":["Milan, Italy"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Andrea","family":"Assanelli","sequence":"additional","affiliation":[{"name":"Hematology and Bone Marrow Transplantation Unit, San Raffaele Scientific Institute IRCCS","place":["Milan, Italy"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Donald","family":"Bunjes","sequence":"additional","affiliation":[{"name":"Department of Internal Medicine III, University Hospital of Ulm","place":["Ulm, Germany"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fabio","family":"Ciceri","sequence":"additional","affiliation":[{"name":"Universit\u00e0 Vita-Salute San Raffaele","place":["Milan, Italy"]},{"name":"Hematology and Bone Marrow 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