In a cohort of 106 donors, we analyzed correlations in the binding of natural antibodies to human glycans in a composition of the glycan array. Along with trivial relationships (between structurally similar gly- cans), we found a high positive correlation between completely unrelated glycans. The most intriguing among the negative is the correlation of average strength (close to –0.5) between antibodies to Galβ1-3GlcNAc and antibodies to lactosamines (Galβ1-4GlcNAc)n. The reason for the functional antagonism between these antibodies is not yet clear.