Fig. 1
From: Age-associated changes in the circulating human antibody repertoire are upregulated in autoimmunity
Antibodies isolated from human sera show different binding profiles in older compared to younger donors. a Peptide arrays were manufactured with over 131 k diverse probes to assess IgG antibody binding. The assay workflow includes incubating donor serum sample on the peptide microarray, detecting bound IgG with a fluorophore-conjugated secondary antibody, and quantifying the fluorescent signal at each feature. A subset of four peptide features are shown along with cognate binding antibody molecules (as indicated by color). b The donor cohorts were designed to obtain diverse sampling of donor demographics, including age, BMI, sex, and geography from multisite recruitment. Combinations of age and BMI were explicitly balanced, as were other combinations of demographics. c Age (x-axis) is highly correlated with many probes’ fluorescent intensities; for example, probe XY064981 with peptide sequence SSVYDG (y-axis) fluorescent intensity and age across N = 601 donors (each datapoint) has Pearson’s correlation coefficient of r = 0.50 (p < 10− 38). d There are 100 s of peptide features that are significantly associated with older vs. younger serum donors (red points). The average peptide intensity of younger donors (x-axis) versus older donors (y-axis) shows the differential expression of all peptides. Every data point is a single peptide probe on the array. Alternative estimates of effect size and significance yield similar results (Figure S1). e Probes associated with age are highly correlated: if one age-associated peptide probe has elevated fluorescent intensity in a given donor, it is likely that fluorescence of many age-associated peptides are increased. Age-associated probes (y-axis, selected red points in Fig. 1d) are shown across all 601 donors in the cohort (x-axis). Donors are labeled by age (gray-scale legend) and probe intensities values are shown as Log10 ratio of probe in specific donor versus mean probe intensity across all donors. Hierarchical clustering was performed on donors and probes independently