Selective increased presentation of type II collagen by leupeptin

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Type II collagen (CII) is an arthritogenic self-antigen in DBA/1 mice.
• Understanding the intracellular processing of CII by antigen-presenting cells (APCs) is crucial for autoimmune disease research.

Purpose of the Study:

• To investigate the intracellular processing of Type II collagen (CII) in the context of I-Aq molecules.
• To analyze the role of protease inhibitors in antigen presentation by hybrid APCs.

Main Methods:

• Generation of hybrid APCs by fusing B lymphoma cells with CII-primed spleen cells.
• Inhibition of protein transport using brefeldin A.
• Treatment with leupeptin, a protease inhibitor, to assess its effect on antigen presentation.
• Pulse-chase analysis and immunoprecipitation to study protein processing and class II molecule formation.

Main Results:

• Intracellular processing and cleavage of CII are required for presentation by APCs.
• Brefeldin A inhibited CII presentation, indicating dependence on new I-Aq molecule synthesis.
• Leupeptin enhanced CII-specific T cell responses in hybrid B lymphomas and immune B cells.
• Leupeptin abrogated ovalbumin presentation but did not affect invariant chain processing or class II dimer formation.

Conclusions:

• Leupeptin enhances CII presentation by protecting epitopes from intracellular proteases.
• The intracellular handling of CII by B cells differs from that of macrophages and total spleen cells.
• These findings provide insights into the mechanisms of self-antigen processing and presentation in autoimmune diseases.