Regulation of murine splenic B cell CR3 expression by complement component 3

Area of Science:

• Immunology
• Molecular Biology

Background:

• Complement component 3 (C3) is crucial for innate and adaptive immunity.
• C3 cleavage products activate B cells via complement receptors CD21/35.
• Discrepancies in B cell responses between CD21/35(-/-) and C3(-/-) mice suggest additional C3 roles.

Purpose of the Study:

• To investigate the role of C3 in regulating complement receptor 3 (CR3) expression on splenic B cells.
• To understand how C3 deficiency impacts CR3 expression and CD11b/Itgam transcript levels.

Main Methods:

• Analysis of splenic B cells from wild-type (WT) and C3(-/-) mice.
• Gene transcript analysis for CR3/CD11b/Itgam.
• Adoptive transfer experiments with splenic B cells and macrophages between WT and C3(-/-) mice.

Main Results:

• C3(-/-) mice exhibit increased cell surface CR3 expression on splenic B cells compared to WT.
• B cells from C3(-/-) mice show 2- to 3-fold higher CD11b/Itgam transcript levels.
• Adoptive transfer confirmed that a C3-deficient environment induces CR3 expression, while C3 presence suppresses it.

Conclusions:

• C3 plays a regulatory role in CR3 expression on splenic B cells.
• C3 influences CR3 levels by modulating CD11b alpha integrin transcript expression.
• These findings reveal a novel mechanism of C3-mediated immune regulation in B cells.