Anti-Mac-1 selectively inhibits the mouse and human type three complement receptor

Area of Science:

• Immunology
• Cell Biology

Background:

• Macrophages and polymorphonuclear leukocytes (PMNL) play key roles in immune responses.
• Complement receptors mediate crucial cellular functions, including phagocytosis and inflammation.

Purpose of the Study:

• To investigate the function of the Mac-1 antigen on immune cells.
• To determine if Mac-1 is involved in complement receptor-mediated interactions.

Main Methods:

• Utilized a rat monoclonal antibody, anti-Mac-1 (M1/70), to target the Mac-1 antigen.
• Assessed the antibody's effect on complement receptor-mediated rosetting of erythrocytes by murine macrophages and human PMNL.
• Tested specificity using erythrocytes coated with C3b (EC3b) and C3bi (EC3bi) fragments.

Main Results:

• Anti-Mac-1 selectively inhibited complement receptor-mediated rosetting by macrophages and PMNL.
• The antibody blocked rosetting with C3bi-coated erythrocytes (EC3bi), indicating involvement with CR3.
• No inhibition of Fc receptor-mediated rosetting was observed.

Conclusions:

• Mac-1 is either identical to or closely associated with the complement receptor 3 (CR3).
• This study provides early evidence linking a monoclonal antibody-defined differentiation antigen to a specific cell surface function.