Fig. 1

Plasma peptidomics of patients with LCH-RO (−). (a) Blue and red lines indicate integrated MS spectra of each MS-LCH and SS-LCH sample, respectively. All plasma sample measurements were repeated four times. The resulting 29 MS spectra per each measurement were combined using flexAnalysis version 2.4 to generate an integrated MS spectrum. Statistical analysis indicated that 32 peptide peaks differed significantly between MS-LCH and SS-LCH patients at an average m/z of <6000. Peaks (arbitrary unit [a.u.]) in the range of m/z 2000–5000, which contains m/z 3145 (arrow), are shown. (b) Blue and red lines indicate each MS spectrum of MS-LCH and SS-LCH samples, respectively. Peaks in the range of m/z 3127–3162, which contains m/z 3145 (arrow), are shown. (c) Blood samples containing the highest concentrations of the target peptide m/z 3145 were used for further identification studies. MS/MS spectra of the target peptides were obtained via LC-MS/MS (Q Exactive). The MS/MS fragmentation data of m/z 3145 were applied to a “nonredundant” human database search (both NCBInr and Swiss-Prot) using MASCOT MS/MS ions search program version 2.1.0 in Biotools software. MS/MS fragmentations of NFRPGVLSSRQLGLPGPPDVPDHAAYHPF, a peptide found in inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4, [PDB: Q14624]), were detected (ion score: 89; expect: 0.00062). Y-axis: relative intensity. (d) A profile summary of peptide fragment m/z 3145 (ITIH4). The amino acid sequence is presented according to the Paris Convention guidelines for peptidomics data presentation. (e) Peptidomics data indicating the intensities of m/z 3145 (ITIH4 fragment) in MS-LCH, SS-LCH, and non-LCH plasma samples were plotted as box-whisker plots. For the MS-LCH, SS-LCH, and non-LCH samples, the median intensities are 15710.537, 2412.950, and 14157.62538, lower quartiles are 4081.623, 1583.592, and 12148.52916, and upper quartiles are 17688.457, 3635.496, and 20523.77099, respectively. P values (Student’s t-test) are also indicated (An asterisk means P > 0.05. A double asterisk means P < 0.05. A triple asterisk means P < 0.01). LCH-RO (−), LCH with no involvement of high-risk organ (spleen, liver, and bone marrow)