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Abstract
Slowly progressing subcutaneous nodules all over the body were detected in 1994 in an otherwise healthy, now 66-year-old woman (UNK). A first biopsy was taken 10 years ago and revealed amyloid. Immunohistochemistry was suggestive for ALκ. From a nodular excisate, performed in the same year for cosmetic reasons, amyloid fibrils were extracted. Protein separation according to their size revealed multiple protein fragments below the MW of an intact κ-light chain. They were identified as κ-fragments by Western blotting. The κ-fragments were cleaved into overlapping peptides using tryptic, N-Asp and chymotryptic digests. Peptides were sequenced by Edman-degradation and mass spectrometry. The complete amino acid sequence of the variable region and most of the constant region of ALκ (UNK) was identified in various fragments comprising positions 1 to 207 of a monoclonal κI-light chain. Four novel and several rare amino acid exchanges have been identified as compared to 17 amyloidogenic and >100 non-amyloidogenic κI-sequences published, leading to increased hydrophobicity of ALκ (UNK). Sequence analysis of C-region peptides allowed one to determine the κ-allotype as being invb+.
A rabbit antibody was produced against ALκI (UNK). It strongly reacted with amyloid on formalin-fixed paraffin embedded tissue sections of the same patient and detected ALκ-amyloid of many other patients. In contrast, antibodies produced against κBJP of subclasses κI–κIV failed to label ALκ (UNK) amyloid deposits.
The patient continues to be free of systemic disease, already for 14 years until today.
| Abbreviations | ||
| ALλ/ALκ | = | amyloid of immunoglobulin λ/κ light chain origin |
| AHγ | = | amyloid of immunoglobulin γ heavy chain origin |
| Aβ2M | = | amyloid of β2 - microglobulin origin |
| AA | = | amyloid of (apo)serum AA origin |
| κBJP | = | κ Bence–Jones proteins |
| UNK (and other three capital letters) | = | identification of patient (artificial acronym) |
| Abbreviations | ||
| ALλ/ALκ | = | amyloid of immunoglobulin λ/κ light chain origin |
| AHγ | = | amyloid of immunoglobulin γ heavy chain origin |
| Aβ2M | = | amyloid of β2 - microglobulin origin |
| AA | = | amyloid of (apo)serum AA origin |
| κBJP | = | κ Bence–Jones proteins |
| UNK (and other three capital letters) | = | identification of patient (artificial acronym) |
Acknowledgements
Laboratory space for this work was kindly provided by Prof. Dr. R. Huber (Director Emeritus) of the Max-Planck-Institute of Biochemistry in Martinsried near Munich. For technical assistance, we thank Ms. M. Zabowa, Ms. J. Lindemayer, Ms. R. Oos and Ms. M. Bandmann. For a recent serum specimen of the patient we thank Dr. B. Gerstenmaier, Berlin; for the performance of a serum free-light-chain assay we thank Dr. M. Zorn, Heidelberg.
Declaration of interest: Dr. Reinhold P. Linke is the owner of amYmed.
Notes
*Added in proof: After this paper had been “accepted with changes” the following paper was “accepted for print”.
Linke, R.P.: Improved classification of various amyloid diseases using validated antibodies and Congo red fluorescence. Immunohistochemical typing of 663 patients. Arch Path Lab. Med. 134 (March 2010; ‘Invited Review’, in print).