Fig. 6: Correlations between neutrophil opsonic phagocytosis, FcγR-binding and CSP-specific IgG subclasses in the Kenyan adult cohort.

A Among Kenyan samples (n = 104), levels of opsonic phagocytosis were significantly correlated with FcγRIIa binding and FcγRIII binding. B–D Antibody-mediated FcγRIIa binding, FcγRIII binding and opsonic phagocytosis were positively correlated with IgG (B), IgG1 (C) and IgG3 (D) reactivity to CSP among samples. All correlations were statistically significant (P < 0.001, Spearman’s correlation). E Samples (n = 104) with higher opsonic phagocytosis activity (defined as greater than the median) showed higher levels of total IgG to full-length CSP (P < 0.001, two-way ANOVA), the NANP repeat region (P = 0.001, two-way ANOVA), the C-terminal region (P < 0.001, two-way ANOVA) and the N-terminal region (P < 0.001, two-way ANOVA) compared to samples with lower opsonic phagocytosis. FcγRIIa and FcγRIII binding by antibodies to CSP was also significantly higher among individuals with high opsonic phagocytosis (P < 0.001 and P < 0.001 respectively, two-way ANOVA). The levels of CSP-specific IgG2 and IgG3 against were significantly higher in samples with high opsonic phagocytosis (P = 0.0464 and P < 0.001 respectively, two-way ANOVA), but not clearly higher for IgG1 (P = 0.106, two-way ANOVA) and IgG4 (P > 0.999, two-way ANOVA). The solid and dotted lines represent the linear regression line and 95% confidence intervals. Boxes and whiskers indicate the medians and interquartile range (IQR) and 1.5 × IQR of each group. Values exceeding this range are presented as dots. Asterisks indicate statistically significant levels (*P < 0.05, **P < 0.01).