Augmenting immune reconstitution after adult allo-haematopoietic stem cell transplantation: current developments and modifiable determinants.

Abstract

Immune reconstitution after adult allogeneic haematopoietic stem cell transplantation (allo-HSCT) shapes infection risk, vaccine responsiveness, relapse and nonrelapse mortality. Advances in graft-vs.-host disease (GvHD) prophylaxis, serotherapy exposure management, cytomegalovirus (CMV) control, functional immune monitoring and adoptive cellular therapy have changed which aspects of recovery can be modified and which augmentors are realistic in current practice. This review sets out what has evolved in adult practice and where intervention can now improve it. GvHD prophylaxis, serotherapy dosing and CMV prophylaxis can increasingly be tuned to individual risk rather than applied uniformly, and exposure-guided and function-based measures are beginning to supplement simple subset counts. Adoptive approaches such as virus-specific T-cells offer targeted immune replacement in refractory viral disease, while thymic regeneration and cytokine-based strategies remain investigational. Updated vaccination guidance and recent immunogenicity data are sharpening humoral monitoring. Taken together, these developments point towards a move from numerical subset counts to function- and exposure-guided assessment of immune reconstitution. Several determinants, including serotherapy exposure, GvHD prophylaxis, CMV control, microbiome preservation and selective adoptive immune replacement, now support individualised decisions, although prospectively validated intervention thresholds remain few.