Disclosed are compositions and related methods of recapitulating bone marrow stroma using scaffold materials (e.g., a porous alginate hydrogel scaffold) containing one or more cellular differentiation factors, and one or more growth factors. Such methods and compositions promote the formation of an ectopic nodule or site that can improve transplanted cell engraftment and selectively drive the development of lymphocytes and the reconstitution of the adaptive immunity after hematopoietic stem cell transplant.