Concentrations of three hapten-binding immunoglobulins in pooled normal human serum

The amount of natural anti-DNP-cap, anti-NIP-cap or anti-ABA-TYR in human IgM was measured by using immunoabsorbents and hapten elution. We found that 1.0% of pooled human IgM is specific for DNP-cap, 0.2% for NIP-cap and 0.02% for ABA-TYR. Haptens NIP and DNP were found to be cross-reactive when tested with natural antibodies even though they were not cross-reactive when tested with immune antibodies.