This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Amyloidosis, Subject name: Pathology
Major fibril protein in Primary Amyloidosis is? 
Select and explain. 
A. AL, B. AA, C. Transthyretin, D. Procalcitonin
A: AL
Answer: A: AL 
Explanation: Ans. (a) AL(Ref: Robbins 9th/pg 257-260)AL protein is made of complete Ig light chains, amino- terminal fragments of light chains, or both.Most of the AL proteins are composed of l light chains or their fragments, but in some cases k chainsThe amyloid fibril protein of the AL type is produced from free Ig light chains secreted by a monoclonal population of plasma cells, like multiple myeloma.