Activation of the classical complement pathway by a polysaccharide from sugar cane

Area of Science:

• Immunology
• Biochemistry

Background:

• The complement system is a crucial part of innate immunity.
• Polysaccharides can modulate immune responses.
• Sugar cane contains various bioactive compounds.

Purpose of the Study:

• To investigate the effects of a sugar cane-derived polysaccharide, Bo, on the human and guinea pig complement system.
• To elucidate the mechanism by which Bo activates complement.

Main Methods:

• In vitro complement activation assays using human and guinea pig serum.
• In vivo complement consumption studies in guinea pigs.
• Investigation of the role of calcium ions (Ca++) and C1q in Bo-mediated activation.
• Use of C1q-deficient serum and purified immunoglobulins.

Main Results:

• Bo, a glucan polysaccharide, activates complement via the classical pathway in human and guinea pig serum.
• Complement consumption (C1, C4, C2, C3) occurs in vivo after Bo injection.
• Activation is dependent on Ca++ ions and C1q, indicating it's not a direct C1s activation.
• Bo-mediated complement activation is restored by adding C1q to deficient serum.
• The alternative complement pathway is minimally affected.
• Activation appears to be mediated by immune complex formation between Bo and natural immunoglobulins.

Conclusions:

• Bo activates the classical complement pathway through immune complex formation with immunoglobulins.
• This mechanism is dependent on C1q and Ca++ ions.
• Bo demonstrates immunostimulating properties by activating the complement cascade.