Abstract. The results reported establish a cellular basis for the inverse relationship between the net electrical charge of immunogens and of the antibodies provoked by them. Glass bead columns were used to reduce the number of immunocompetent spleen cells preferentially reactive with more acidic immunogens. After a single immunization, titers of antibodies to an acidic dinitrophenylated copolymer of tyrosine, glutamic acid, and lysine (DNP-901) elicited in recipient mice by filtered spleen cells were significantly lower than those generated by unfiltered cells. After secondary stimulation, the major portion of the antibodies provoked by the acidic antigen was found in the more acidic fraction eluted from DEAE-Sephadex, in contrast to the more basic antibodies, of the same specificity, generated by unfiltered spleen cells. Results obtained by transplanting a limiting number of spleen cells indicate a depletion in the number of precursor cells reactive with dinitrophenyl on DNP-901 after glass bead chromatography, whereas there was no change in the response to dinitrophenyl on a basic copolymer, DNP-912, containing the same amino acids in different molar ratios.The inverse relationship between the net electric charge of immunogenic macromolecules and the net charge of antibodies provoked by them has been demonstrated for antibodies produced in rabbits1'2, mice3, goats4, and humans5, and is valid for antibodies of IgG6, IgM7, and, probably, IgEl class. Thus, e.g., antibodies to the acidic diphtheria toxoid and to negatively-charged synthetic copolymers of amino acids appear mainly under the first peak upon fractionation on DEAE-Sephadex 8, whereas antibodies to the basic lysozyme and positivelycharged amino acid copolymers appear predominantly, or exclusively, under the second peak 3.Haptens such as the dinitrophenyl group1 2 or a peptide of L-alanine (unpublished data of Licht, A., B. Schechter, I. Schechter, and M. Sela) will lead to antibodies fractionating under the first or the second DEAE-Sephadex peak, depending on whether they are attached to a negatively or positively charged carrier. The anti-hapten antibodies produced upon immunization with such conjugates differ in their net electric charge, but not in their specificity or affinity, as measured by means of small molecules related chemically to the original haptens. The inverse correlation described depends on the net electric charge of the intact immunogen, and not on the net charge within a limited area around the anti-1288