The follicular dendritic cell restricted epitope, FDC-M2, is complement C4; localization of immune complexes in mouse...

Area of Science:

• Immunology
• Complement System Biology

Background:

• Follicular dendritic cells (FDCs) are crucial for adaptive immunity.
• The FDC-M2 marker, recognized by mAb209, has been used to study FDCs.
• The precise identity and function of FDC-M2 have remained unclear.

Purpose of the Study:

• To identify the molecular nature of the murine FDC marker FDC-M2.
• To investigate the role of FDC-M2 in immune complex-mediated inflammation and clearance.
• To evaluate mAb209 as a tool for studying complement deposition in vivo.

Main Methods:

• Immunohistochemistry using mAb209 on wild-type and complement-deficient mice.
• Analysis of FDC-M2 distribution in various tissues, particularly at sites of inflammation.
• Comparison of immune complex deposition and clearance in different complement-deficient models.

Main Results:

• The FDC-M2 marker was identified as complement component C4.
• FDC-M2 (C4) was detected at sites of immune complex-mediated inflammation.
• Distinct populations of FDC-M2+ cells in the spleen, separate from FDCs, were involved in immune complex capture.

Conclusions:

• Monoclonal antibody mAb209 recognizes complement component C4, not solely an FDC-specific protein.
• mAb209 is a valuable tool for analyzing complement deposition and immune complex dynamics in vivo.
• The study reveals novel roles for FDC-M2+ cells in immune complex handling beyond traditional FDCs.