Lower T-Cell Subset Counts Seen With More Severe COVID-19

By Reuters Staff

May 15, 2020

NEW YORK (Reuters Health) — Low T-cell subset counts, especially of CD4+ and CD8+ T cells, are associated with more severe illness in patients with COVID-19, researchers in China report.

Low lymphocyte counts have been reported in association with severe COVID-19, but little is known about changes of lymphocyte subsets in peripheral blood during the course of COVID-19 infection.

Dr. LaGen Wan and colleagues of the First Affiliated Hospital of Nanchang University investigated the counts of lymphocyte subsets in 103 COVID-19 patients (median age, 46 years) and the significance of different lymphocyte subsets during the course of infection.

Most patients (86/103) had mild-to-moderate illness, while 17 had severe disease and were treated in the intensive-care unit (ICU). The control group included 13 healthy controls who had no infectious disease and were unrelated to the patients enrolled in the study.

COVID-19 patients had significant decreases in the counts of CD3+, CD4+, and CD8+ T cells and in natural killer (NK) cells, as well as increases in the CD4/CD8 ratio, but B-cell counts did not differ significantly from those in the control group.

Compared with patients with mild-to-moderate illness, patients with severe COVID-19 had significantly lower CD3+, CD4+, and CD8+ T-cell counts, the researchers report in the Journal of Infectious Diseases.

During follow-up, CD3+, CD4+, and CD8+ T-cell counts recovered dramatically in most patients whose SARS-CoV-2 nucleic acid tests turned negative but did not change significantly in patients with persistently positive tests. NK and B-cell counts did not change significantly during follow-up.

CD8+ T-cell counts best discriminated between COVID-19 patients and healthy controls, whereas CD4+ T-cell counts were slightly more accurate for differentiating between patients with severe illness and patients with mild-to-moderate illness. In both cases, the combination of CD8+ and CD4+ T-cell counts proved more accurate than either T-cell count alone.

"The counts of CD8+ and CD4+ T cells can be used as diagnostic markers of COVID-19 and predictors of disease severity," the authors conclude.

"Immunological characteristics of the lymphocyte subsets are important for exploring the mechanisms underlying SARS-CoV-2 infection," they add. "Large-scale multicenter clinical studies are needed to elucidate lymphocyte subsets in the immunological mechanisms of COVID-19."

Dr. Wan and coauthors Dr. AiPing Le and Dr. JunMing Li did not respond to a request for comments.

SOURCE: https://bit.ly/3bslRJ9 Journal of Infectious Diseases, online May 7, 2020.