The ability of the adaptive immune system to form memory is key to providing protection against secondary infections. Resident memory T cells (T RM ) are specialized T cell populations that reside within tissue sites where they await reencounter with their cognate antigen. T RM are distinct from circulating memory cells, including central and effector memory T cells, both functionally and transcriptionally. Since the discovery of T RM , most research has focused on CD8 + T RM , despite that CD4 + T RM are also abundant in most tissues. In the past few years, more evidence has emerged that CD4 + T RM can contribute both protective and pathogenic roles in disease. A complexity inherent to the CD4 + T RM field is the ability of CD4 + T cells to polarize into a multitude of distinct subsets and recognize not only viruses and intracellular bacteria but also extracellular bacteria, fungi, and parasites. In this review, we outline the key features of CD4 + T RM in health and disease, including their contributions to protection against SARS-CoV-2 and potential contributions to immunopathology associated with COVID-19.

中文翻译：

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同一枚硬币的两个方面：保护性与致病性 CD4 + 常驻记忆 T 细胞

适应性免疫系统形成记忆的能力是防止继发感染的关键。常驻记忆 T 细胞 (TR M) 是专门的 T 细胞群，它们驻留在组织部位等待与它们的同源抗原再次相遇。吨R M与循环记忆细胞不同，包括中枢和效应记忆 T 细胞，无论是在功能上还是在转录上。自从发现 TR M, 大多数研究都集中在 CD8+吨R M，尽管 CD4+吨R M在大多数组织中也很丰富。在过去几年中，出现了更多证据表明 CD4+吨R M可以在疾病中发挥保护作用和致病作用。CD4 固有的复杂性+吨R M场是CD4的能力+T 细胞极化成许多不同的亚群，不仅识别病毒和细胞内细菌，而且识别细胞外细菌、真菌和寄生虫。在这篇评论中，我们概述了 CD4 的主要特征+吨R M在健康和疾病方面，包括他们对预防 SARS-CoV-2 的贡献以及对与 COVID-19 相关的免疫病理学的潜在贡献。