Abstract
Sucrose density gradient isoelectric focusing was modified to micro-scale to facilitate analysis of nanogram amounts of IgM and IgG anti-hapten antibodies. This modification was utilized to characterize the antibody produced by neonatal splenic foci against the haptenic dinitrophenyl (DNP) determinant. Such neonatal ‘monofocal’ antibodies had restricted isoelectric spectra, implying their origin from the clonal progeny of a single antibody-forming precursor cell. The majority of neonatal ‘monofocal’ antibodies characterized with respect to isoelectric point and immunoglobulin class were dissimilar, thus indicating diversity in the neonatal precursor cell population.