Effect of red seaweed sulfated galactans on initial steps of complement activation in vitro

Sokolova, E. V.; Kravchenko, A. O.; Sergeeva, N. V.; Kalinovsky, A. I.; Glazunov, V. P.; Bogdanovich, L. N.; Yermak, I. M.

The research described here presents data on the effect of galactans of red algae, carrageenans (λ/μ/ν-, κ-, κ/β-, and ι/κ-types), and agar on complement system activation in normal human serum. The experiments were based on well surfaces coated with complement triggering agents for binding initiating components of the complement system—C3 and C4. The sulfated galactans inhibited C3 binding to lipopolysaccharides with direct dependence on the sulfation degree of polysaccharides. Sulfation degree was also important in carrageenans’ capacity to reduce C4 binding to mannan. However, C4 binding to antibodies was considerably activated by carrageenans, especially with 3,6-anhydrogalactose. The gelling carrageenans were able with more intensity to block antigen binding centers of total serum IgM. No structural characteristics mattered in ameliorating C5 cleavage by plasmin in extrinsic protease complement activation, but λ/μ/ν- and κ/β-carrageenans almost completely inhibited C5 cleavage. Thus, galactans participated in cell surface biology by imitating surface glycans in C3 binding, inhibiting mannose binding lectin, and stimulating classical pathways, probably due to their structure based on carrabiose.