Baseline pulmonary levels of CD8+ T cells and NK cells inversely correlate with expression of the SARS-CoV-2 entry receptor ACE2

Duijf, Pascal H.G.

Coronavirus disease 19 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and currently has detrimental human health, community and economic impacts around the world. In SARS-CoV-2-infected lung, induction of immune cell-recruiting cytokines is initially poor. When induction does occur, this may in fact exacerbate infection. These observations suggest that baseline levels of leukocytes, already residing in the lung prior to infection, may be important for orchestrating an effective early immune response. Hence, we performed “in silico flow cytometry” on 1,927 human lung tissues to deconvolute the levels of seven leukocyte types involved in triggering an acute anti-viral cellular immune response. Baseline levels of CD8+ T cells, resting natural killer (NK) cells and activated NK cells are significantly lower in lung tissues with high expression of the SARS-CoV-2 host cell entry receptor ACE2. We observe this in univariate analyses, in multivariate analyses that include sex, age, race, body mass index and smoking history, and in two independent datasets. Elevated ACE2 expression increases sensitivity to coronavirus infection. Thus, our results suggest that a subgroup of individuals may be exceedingly susceptible to COVID-19 due to concomitant high preexisting ACE2 expression and low baseline cytotoxic lymphocyte levels in the lung.