Sequence determinations of tryptic peptides derived from amyloidogenic proteins were performed using MALDI-MSMS analysis directly from Congo red positive regions in tissue sections with/without procedure for retrieval of epitopes before on-tissue digestion.
Tryptic peptides, m/z = 1073.5 and 1924.3 were identified with the sequences, from 48th to 56th and 1st to 19th positions of Ig lambda V-III region, respectively. Other peptides, m/z = 1365.5 and 1523.5 were with the sequences, from 22nd to 34th and 36th to 48th positions of TTR, respectively. Heat-map images of all four tryptic peptides were overlapped with Congo red positive regions. Immunohistochemistry of FFPE tissue sections was confirmed to only react with anti-¦Ë chain antibody in a case of AL-type amyloidosis or anti-TTR antibody in two cases of TTR-type amyloidosis.
IMS with MSMS analysis using on-tissue tryptic digestion enables us not only to identify amyloidogenic molecule in a sliced tissue section but also to play a complementary role with the conventional pathological examination.