Fig. 3.

Increased levels of IL-6 in critical coronavirus disease 2019 patients. A) Levels of cytokines were determined in serum samples of non-intubated and intubated coronavirus disease 2019 patients by standard immunoassay. i) IL-1β ii) IL-6, iii) IL-8 and iv) IL-10. v) ratio of IL-6:IL-10. B) The levels of the same cytokines for patients upon recovery. C) A positive correlation of IL-6 with i) Natural Killer cells and ii) Natural Killer-like T cells was observed. Statistical analysis was performed by Student's t-test, Mann-Whitney U test or Wilcoxon test where applicable. *p < 0.05, **p < 0.01. Spearman correlation was performed for correlation analyses. Normal range values for cytokines as stated in technical bulletin of the ELISA kit used were as follows: 1.1–14.3 pg/ml for IL-6, 7.9–12.9 pg/ml for IL-10, and 34.8–666.4 pg/ml for IL-8. IL-1β was reported as undetectable in healthy human samples and one positive sample showed a value of 8.7 pg/ml.