Lymphoproliferation in type II mixed cryoglobulinemia

Area of Science:

• Immunology
• Hepatology
• Oncology

Background:

• The established role of Hepatitis C virus (HCV) in type II mixed cryoglobulinemia (MC) etiology necessitates further elucidation of its pathogenetic links with immune responses and lymphoproliferation.
• Understanding the interplay between HCV, immune system dysregulation, MC natural history, and lymphoproliferative processes in bone marrow and liver is crucial.

Purpose of the Study:

• To investigate the pathogenetic relationships among HCV, immune system, MC natural history, and lymphoproliferation in bone marrow and liver.
• To characterize lymphoid infiltrates in bone marrow and liver biopsies of patients with HCV-positive type II MC compared to controls.

Main Methods:

• Histological and immunohistochemical examination of bone marrow and liver specimens from 82 patients with HCV-positive type II MC and 20 controls with chronic hepatitis C.
• Analysis focused on disease behavior markers, including bcl-2 oncogene product and Ki67 proliferation antigen expression.

Main Results:

• MC patients exhibited bone marrow lymphoid infiltrates with monomorphic cytology, immunoglobulin light chain monotypic restriction, bcl-2 expression, and low proliferation (Ki-67 < 3%).
• Non-cryoglobulinemic patients showed reactive lymphoplasmacytosis in bone marrow.
• Liver biopsies in both groups revealed portal T-cell infiltrates with a significant B-cell component, particularly in MC patients, often forming pseudo-follicles. These B-cells expressed bcl-2 and CD5, with MC patients showing frequent monotypic IgM kappa restriction.

Conclusions:

• Findings support a lymphoproliferative disorder in type II MC pathogenesis, characterized by B-cell accumulation due to inhibited apoptosis and low proliferation, explaining the indolent course.
• HCV likely interacts with these B-cells, promoting their clonal expansion and contributing to MC pathology.