The curative potential of non-autologous cellular therapy is hindered by the requirement of anti-rejection therapy. Cellular encapsulation within nondegradable biomaterials has the potential to inhibit immune rejection, but the efficacy of this approach in robust preclinical and clinical models remains poor. While the responses of innate immune cells to the encapsulating material have been characterized, little attention has been paid to the contributions of adaptive immunity in encapsulated graft destabilization. Avoiding the limitations of animal models, we established an efficient, antigen-specific in vitro platform capable of delineating direct and indirect host T cell recognition to microencapsulated cellular grafts and evaluated their consequential impacts. Using ovalbumin (OVA) as a model antigen, we determined that alginate microencapsulation abrogates direct CD8⁺ T cell activation by interrupting donor-host interaction; however, indirect T cell activation, mediated by host antigen presenting cells (APCs) primed with shed donor antigens, still occurs. These activated T cells imparted cytotoxicity on the encapsulated cells, likely via diffusion of cytotoxic solutes. Overall, this platform delivers unique mechanistic insight into the impacts of hydrogel encapsulation on host adaptive immune responses, comprehensively addressing a long-standing hypothesis of the field. Furthermore, it provides an efficient benchtop screening tool for the investigation of new encapsulation methods and/or synergistic immunomodulatory agents.

非自体细胞疗法的治疗潜力因抗排斥疗法的要求而受到阻碍。不可降解生物材料内的细胞封装具有抑制免疫排斥的潜力，但这种方法在稳健的临床前和临床模型中的功效仍然很差。虽然先天免疫细胞对封装材料的反应已经被表征，但很少有人关注适应性免疫在封装移植物不稳定中的作用。为了避免动物模型的局限性，我们建立了一个高效的、抗原特异性的体外平台，能够描述宿主 T 细胞对微囊细胞移植物的直接和间接识别，并评估其间接影响。使用卵清蛋白 (OVA) 作为模型抗原，我们确定藻酸盐微胶囊化通过中断供体-宿主相互作用来消除直接 CD8 ⁺ T 细胞激活；然而，由脱落的供体抗原引发的宿主抗原呈递细胞 (APC) 介导的间接 T 细胞激活仍然会发生。这些活化的 T 细胞可能通过细胞毒性溶质的扩散对封装的细胞产生细胞毒性。总体而言，该平台提供了关于水凝胶封装对宿主适应性免疫反应影响的独特机制见解，全面解决了该领域长期存在的假设。此外，它还为研究新的封装方法和/或协同免疫调节剂提供了有效的台式筛选工具。