Fig. 6.

MHC-II independent upregulation of CD74 in T cells of critically ill COVID-19 patients. A, B Increased inflammatory markers CRP and IL-6 in patients with severe COVID-19 disease. Serum peak concentrations of inflammatory markers CRP (mg/dl) and IL-6 (pg/ml) from laboratory results of patients with mild (WHO 1–3, n = 18) vs. severe (WHO ≥ 5, n = 12) COVID-19 disease. C–F CD74 and CXCR4 surface expression on CD4⁺ and CD8⁺ T cells from mild vs. severe disease patients. G No significant differences in HLA-DR surface expression in COVID-19 patient cohorts classified by disease severity. Results of a flow cytometry-based cell surface receptor profiling. Bar charts in A–G show means ± SD with individual datapoints representing independent patients. Cell surface receptor-positive cells are plotted as percentages of the respective T-cell phenotype. Statistical differences were analyzed by unpaired t test for A and C and Mann–Whitney U test for B, D, E, F, and G and indicated by actual P values.