**Core Concept**
Amyloidosis with immunocyte dyscrasias involves the deposition of abnormal proteins, leading to tissue damage and organ dysfunction. The chemical nature of these amyloid deposits is crucial in understanding the pathophysiology of the disease.

**Why the Correct Answer is Right**
The amyloid deposits in immunocyte dyscrasias, such as multiple myeloma or Waldenström's macroglobulinemia, are primarily composed of immunoglobulin light chains. These light chains are produced by the malignant plasma cells and accumulate in tissues, leading to amyloidosis. The immunoglobulin light chains are rich in cysteine residues, which form disulfide bonds, contributing to the fibril formation and amyloid deposition.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the chemical nature of the amyloid deposits in immunocyte dyscrasias. While amyloid deposits can be composed of various proteins, the correct answer focuses on immunoglobulin light chains.
**Option B:** This option is incorrect because it refers to amyloid deposits in Alzheimer's disease, which are primarily composed of amyloid-β peptides, not immunoglobulin light chains.
**Option C:** This option is incorrect because it is too broad and does not specify the chemical nature of the amyloid deposits in immunocyte dyscrasias.

**Clinical Pearl / High-Yield Fact**
Immunoglobulin light chain amyloidosis is a common cause of amyloidosis in patients with multiple myeloma or Waldenström's macroglobulinemia. Early detection and treatment of the underlying plasma cell dyscrasia can prevent or slow the progression of amyloidosis.

**Correct Answer: D. Immunoglobulin light chains.**