Functional diversity of natural IgM

This paper proposes a method for the quantitative characterization of reper toire diversity of an unknown mixture of antibodies on the basis of its rea ctivity profile in the quantitative immunoblot (QIB). The QIB is calibrated by measuring the reactivity profiles of supernatants of known 'diversity' (i.e. known numbers of B cell clones). We define a quantitative 'index of v ariability' (IV) which decreases regularly as the diversity increases and t he profiles tend towards a common 'convergence profile'. The calibration pr ocedure is consolidated by a mathematical model based on the Poisson distri bution; this theoretical model accounts correctly for the observed converge nce behavior. On the basis of this calibration curve, it is possible to est imate the diversity of an unknown antibody mixture from a measure of its IV . We conclude that the functional diversity of natural serum IgM in mice ca n be estimated at similar to 16,000 clones.