CD4 and acute respiratory distress syndrome: Similarly, Weiskopf et al., in their study of 10 COVID-19 patients who developed ARDS, reported that peripheral SARS-CoV-2-specific CD4+ T-cells typically had a central memory phenotype (based on CD45RA and CCR7 expression), whereas the majority of virus-specific CD8+ T-cells had a CCR7- effector memory (TEM) or TEMRA phenotype [49].