2, Cornell University, Ithaca, New York, United States
Antibodies are routinely used as therapeutic agents to fight a wide range of disorders including asthma, blood cancers, breast cancer, arthritis, and transplant rejection. Humoral immunity against infections depends on the germinal center (GC) differentiation process in the B cell follicles of secondary lymphoid organs, such as spleen and lymph nodes. In GCs, B cells rapidly proliferate and somatically mutated high-affinity antibody secreting cells, i.e. plasma cells, are generated from naïve B cells in response to T cell-dependent antigen. To date, the scientific community has relied on animal models to generate high-affinity antibodies and discover fundamental knowledge of GC immunology. Yet we are far from understanding the extracellular and intracellular factors that contribute to the exuberant pace of the GC reaction and conversion to antibody secreting cells (ASCs). Such information would be crucial for developing tranlational therapeutics, understanding the basic cellular nature of humoral immunity, as well as the biology of malignant lymphomas that arise from GC B cells and manifest their highly proliferative phenotype. A major impediment to answering such immunological questions is that GC cells in a mouse model is highly heterogenous and mouse models with silenced epigenetic genes do not develop GCs. Infusion of epigenetic inhibitors cannot enable these studies because GCs are heterogeneous with varying cell cycle phases. Therefore, there is a need for tractable, ex vivo platform that can induce bona fide GC reaction and synchronize nearly all cells in the same GC phase. Here we report the development of hydrogel and nanomaterials based ex vivo immune organoids [1, 2] that recapitulate the complex immunobiology of wild type and transgenic knockout mice, and use this immune tissue model to show that Enhancer of zeste homolog 2 (EZH2) histone methytransferase mediates GC formation through repression of cyclin-dependent kinase inhibitor CDKN1A (p21Cip1). We next describe development of a designer immune organoid, where hydrogels model T cell-like selection process to generate high affinity antibody secreting cells.
 A. Purwada, A. Singh, Immuno-engineered Organoids for Regulating the Kinetics of B cell Development and Antibody Production, Nature Protocols 12 (2017) 168-182.
 W. Beguelin, M.A. Rivas, M.T. Calvo Fernandez, M. Teater, A. Purwada, D. Redmond, H. Shen, M.F. Challman, O. Elemento, A. Singh, A.M. Melnick, EZH2 enables germinal centre formation through epigenetic silencing of CDKN1A and an Rb-E2F1 feedback loop, Nature Communications 8(1) (2017) 877.