Lightly haptenated proteins induce IgM‐deficient antibody responses

Abstract Pairs of hapten‐protein conjugates were used for immunization of different groups of mice. One member of a pair always carried more than 7 moles of hapten per mole of protein (polyvalent conjugate), while the ratio was less than 1.5 for the other member of a pair (mainly monovalent conjugate). The total anti‐hapten response in the two groups of mice was equalized by dose adjustments. Even after this equalization, mice produced 2.3 to 4.3 times higher IgM titers in response to the polyvalent conjugates than to the mainly monovalent ones. A mixture of polyvalent conjugate and noncoupled carrier induced a lower response than the conjugate alone, but both were equally rich in IgM antibody.