Fig. 2

Circulating immunoglobulin concentrations in COVID-19 pneumonia at the time of admission. A The study cohort comprised 366 patients were classified based on the absence (WHO 1; Ambulatory group) or presence of pneumonia (WHO 2–7; Pneumonia group). Blood sampling for ELISA analysis was performed at the time of admission. B Circulating levels of IgM, IgA and IgG in the no pneumonia group (WHO 1; patients without pneumonia, ambulatory group) and COVID-19 pneumonia group (WHO 2–7) measured by ELISA are represented by scatter dot plot with mean (wide line). Statistical differences among groups were determined by the nonparametric Mann–Whitney U-test. C Heatmap showing the point-biserial correlation coefficient (pb) of pairwise comparison analyses between previous comorbidities with levels of the three Igs. The correlation matrix is colour-coded according to the point-biserial correlation coefficient (− 1:1, blue:red through white), and correlations with statistical significance are indicated with an asterisk as *P < 0.05. (D) Individual correlations of each Ig with age in men and (E) women who developed pneumonia (WHO 2–7). Statistical significance are indicated in bold as *P < 0.05