Granulocytes May Weaken the COVID Immune Response

September 10, 2021

Low-density granulocytes (LDG) are a type of white blood cell known to circulate at increased levels in certain autoimmune diseases (such as rheumatoid arthritis) but are still poorly understood in relation to viral infections. The rise of SARS-CoV-2 highlighted the need to investigate these cells and their mechanisms, as they are known to be one of the first cellular responders to infection.

A study recently published in PLOS Pathogens sought to determine the role that LDGs may play in the disease progression of COVID-19. The study included 55 COVID-19 infected patients (34 hospitalized and 21 outpatients), along with 14 healthy age- and sex-matched controls. After measuring LDG levels, the researchers detected a significant increase in LDGs in the blood of COVID-19 patients compared to healthy control subjects and an even more prominent increase in severe COVID-19 cases.

Further testing demonstrated the immunosuppressive capacities of these cells. LDGs are typically associated with the early innate immune response, though researchers found that their involvement in the fight against COVID-19 included inhibition of the proliferation and division of T lymphocytes. This impairment of T lymphocytes subsequently weakens the adaptive immune response against the virus and research has shown that low levels of T lymphocytes are a major indicator of developing a severe COVID-19 case versus a milder infection.