Engineering human immune organoids for translational immunology

Abstract

Animal models have been extensively used as a gold standard in various biological research, including immunological studies. Despite high availability and ease of handling procedure, they inadequately represent complex interactions and unique cellular properties in humans due to inter-species genetic and microenvironmental differences which have resulted in clinical-stage failures. Organoid technology has gained enormous attention as they provide sophisticated insights about tissue architecture and functionality in miniaturized organs. In this review, we describe the use of organoid system to overcome limitations in animal-based investigations, such as physiological mismatch with humans, costly, time-consuming, and low throughput screening. Immune organoids are one of the specific advancements in organogenesis ex vivo, which can reflect human adaptive immunity with more physiologically relevant aspects. We discuss how immune organoids are established from patient-derived lymphoid tissues, as well as their characteristics and functional features to understand immune mechanisms and responses. Also, some bioengineering perspectives are considered for any potential progress of immuno-engineered organoids.

Keywords: Human adaptive immune system; In vitro immune model; Lymphoid organ; Organoids.

Graphical abstract

Fig. 1

Schematic illustration representing the human lymphatic organ modelling studies and the pros and cons between each model, including the in vivo animal testing, organ-on-a-chip system, precision cut tissue slice (PCTS), and organoid culture.

Fig. 2

Existing lymphoid organ models. (A) Functional repopulation of whole-organ human thymus scaffolds. Gross microscopic images of a thymus scaffold after stromal cells injection (top panel) and representative flow cytometry analysis of multicellular compositions from repopulated scaffold after 8 days in culture (below panel). Reproduced under terms of the CC-BY license [59]. Copyright 2020, Nature Portfolio. (B) The design of human bone marrow-on-a-chip consisting of (i) co-culturing concept between perivascular- and vascularized endosteal bone marrow niche, (ii) an illustration of 5-channel microfluidic device and (iii) 96-well plate layout of human bone marrow-on-a-chip. In Fig. 2B(ii), mesenchymal stem cells (MSCs) are differentiated for 21 days in the central channel of the device to generate endosteal layer, followed with human umbilical vein endothelial cells (HUVECs), MSCs, and HSPCs being loaded on top of the endosteal layer and vasculogenesis occurs within 5 days to form the human bone marrow-on-a-chip. Reproduced with permission [72]. Copyright 2021, Elsevier. (C) Schematic diagram of spleen-on-a-chip platform containing macrophage rich zones (M-chip) and splenic inter-endothelial slits (IES) in the wall of sinuses (S-chip) to mimic splenic filtration of altered RBCs. Reproduced under terms of the CC-BY license [83]. Copyright 2023, The Proceedings of the National Academy of Sciences. (D) Lymph node model in vitro. (i) Schematic illustration representing human native lymph node and (ii) requirements and compartmentalization for biomimetic lymph node-on-chip. Reproduced under terms of the CC-BY license [91]. Copyright 2021, Frontiers.

Fig. 3

Overview of the currently established human immune organoid generation methods, including (A) cell co-culturing system, (B) conventional direct cell culture in tissue culture dish, (C) disposable bioreactor system, and (D) Hydrogel scaffolds embedding method. Figure C is reproduced with permission [108]. Copyright 2010, Elsevier.

Fig. 4

Various characterization methods and readouts to evaluate immune organoids. (A) Antibody class-switching and somatic hypermutation analysis to check antibody responses representing physiological functions of immune organoids. Reproduced with permission [134]. Copyright 2019, Elsevier. (B) Multicellular composition and diversity in organoids can be revealed throughout multi-omics analysis. The UMAP projection data was reproduced under terms of the CC-BY license [129]. Copyright 2024, Elsevier. (C) Cytokine release assays could represent the metabolic functions of immune organoids. Reproduced under terms of the CC-BY license [135]. Copyright 2013, MDPI. (D) Histological-, immunohistochemistry-, and immunofluorescence staining are useful to analyse organoid morphological structures that closely resemble its native organ architecture. The immunofluorescence images showing GC formation in the presence of PDPN⁺ FRCs of palatine tonsils was reproduced under terms of the CC-BY license [136]. Inset histochemical- and immunofluorescence staining images within illustrative figure (centre) were reproduced with permission [109]. Copyright 2022, Elsevier.

Fig. 5

Overcoming challenges and future directions on immuno-engineered organoids. Bioengineering approaches for the improvements in (A) organoid architecture and (B) vascularization and maturation levels. (C) A fusion of immune-, cancer-, and blood vessels organoid to form in vitro assembloid model that can reorchestrate tumour microenvironment. (D) A chip-driven immunological model to mimic the whole adaptive human immune system in an in vitro fashion. Multiple types of immune organoids were grown in an integrated microfluidic device to see their synergistic functions in acquiring immune sentinels.