Fig. 2

Analysis of the human antibody response to K. pneumoniae O1 and O2 LPS. a O1 and O2-specific IgG antibodies were measured by ELISA in plasma derived from 103 healthy donors (left panel) and 6 ICU patients (right panel) diagnosed with O2 K. pneumoniae infection. Shown are the endpoint titers based on serial dilutions. Lines between data points indicate data acquired from the same sample. b–d Analysis of antigen-specific repertoires (AMBRA, antigen-specific memory B cell repertoire analysis) from tonsillar IgG and IgM memory B cells of 33 donors (30 of the 33 were available for IgM analysis, Supplementary Fig. 2). Total tonsillar lymphocytes were plated and stimulated with R848 and IL-2 and the 10-day culture supernatants (192 cultures per donor) were analyzed by ELISA for the presence of IgG or IgM antibodies that bind to O1 LPS, O2 LPS or uncoated control plates. The OD values obtained from the analysis of uncoated plates were subtracted from the analysis of the O1 and O2 specific responses. b Shown are ELISA OD values of individual cultures from the analysis of one representative donor. Cut-off values are indicated by a dotted line. O1, O2 and O1/O2 reactive cultures are represented as magenta, blue and orange circles, respectively. c, d Each data point represents the frequency of the cultures (n = 192) scoring as positive for IgG (c) or IgM (d) reactivity to O1 or O2 LPS for each of the donors analyzed, according to the cut-off values shown in b. Data was analyzed using the Wilcoxon matched-pair signed rank test to assess significance. ****p < 0.0001