A particular cutaneous Mo/Mac phenotype in COVID-MDR
Next, we sub-clustered Mo/Mac into 4 subsets (Figure 3C, D). Cells of
cluster III strongly expressed macrophage markers CD16, CD163, CD206 and
the co-stimulatory marker CD40 all of which are associated to innate
immunity. Cluster II cells expressed fewer markers, notably HLA-DR,
CD163 and CD206 and lower activation. Cells of cluster IV were less
activated and expressed the skin homing marker CLA. Clusters I showed
low expression of other myeloid markers and HLA-DR.
Quantification of these Mo/Mac clusters (Figure 3D) revealed phenotypic
diversity between COVID-MDR, DRESS, and MDR. Interestingly, Mo/Mac of
cluster II were highest in COVID-MDR, but also well present in DRESS,
while decreased in MDR and HC. Cells of cluster III were present in
COVID-MDR and MDR but absent in DRESS and HC. A separation of Mo/Mac
cells by indication confirmed the higher expression of CD1c, CD16, CD40,
CD163 and CD206 in the COVID MDR Mo/Mac compartment (Figure S3B). In
summary, activated macrophages expressing the co-stimulatory marker CD40
were often observed in COVID-MDR and may cause the strong activation of
T cells.