Competitive Specificity Analysis of Natural Antibodies against Epitope of Bacterial Cell Wall Peptidoglycoan: Glucosaminylmuramyl Dipeptide Carrying Adjuvant Activity.

The natural antibodies against glucosaminylmuramyl dipeptide (GMDP), the epitope of peptidoglycan of bacterial cell wall, isolated from human serum by thermal extraction possess a capability to cross-react with determinant of glycan chain - tetrasaccharide consisting of N-acetylglucosamine and N-acetylmuramic acid. The intensity of interaction of natural anti-GMDP-antibodies with specific ligand is significantly higher than with tetrasaccharide. The natural antibodies against tetrasaccharide carry properties of heteroclitic antibodies, i.e. the intensity of their interaction with heterologous ligand, GMDP, is significantly higher than with homologous one, tetrasaccharide GMGM. GMDP is supposed to be specific antigenic peptidoglycan determinant against which the antibodies reacting with various intensity to homologous (GMDP) and relative (tetrasaccharide) hapten are formed in the process of natural immunization.

Affinity of Serum Natural Antibodies against Peptidoglycan Bacterial Cell Component with Adjuvant Activity.

We studied affinity of natural antibodies of human serum against glucosaminylmuramyl dipeptide (GMDP), the epitope peptidoglycan bacterial cell wall component which carries adjuvant activity. Antibodies against GMDP were isolated from the blood sera of healthy donors using thermal extraction of antibodies from specific ligand on plastic. Determination of the dissociation constant (K(d)) showed equal K(d) in the serum and affinity-purified anti-GMDP-antibodies, i.e. extraction by this method led to the isolation of all subpopulations of antibodies in spite of their affinity. K(d) of serum, affinity-purified and monoclonal anti-GMDP-antibodies proved of low value - 10(-6) M, and according to this index anti-GMDP-antibodies may be classified between anti-protein and anti-carbohydrate antibodies.