Figure 1

Correlation analysis between the vitamin D and NK/NKT subpopulations of immune cells on admission and on day 7 of stay in the ICU. Baseline levels of vitamin D were positively correlated with NKT cell counts (r = 0.6 (95% CI 0.38; 0.76), P = 0.001), in contrast to NK cells lacking such association (r = 0.26, (95% CI − 0.26; 0.51), P = 0.07) (a,b). On day 7 of treatment, vitamin D levels were positively correlated with NK cell (r = 0.67 (95% CI 0.42; 0.82), P = 0.001) and NKT cell (r = 0.41 (95% CI 0.08; 0.65), P = 0.013) counts (c,d).