Innate Lymphoid Cells in COVID-19: Bystanders or Active Contributors?

The COVID-19 pandemic that was caused by SARS-CoV-2 prompted extensive investigation into the immune mechanisms that drive SARS-CoV-2 clearance and pathogenesis.Of particular interest is the innate immune system, which appears to play a critical role in early defense against SARS-CoV-2, particularly at the mucosal interfaces where it first enters the body.The innate lymphoid cells (ILCs) may be key cellular players in this immune response.These cells comprise the helper ILCs and natural killer (NK) cells and are often referred to as the innate counterparts of T cells.They function as important coordinators of protective immune responses during the early stages of virus infections in general but can sometimes also mediate their pathogenicity.This review discusses the current understanding of how ILCs may contribute to both protective immunity against SARS-CoV-2 infection and the pathological inflammation this virus induces.We address the question: are ILCs mere bystanders or are they active contributors to the immune response?