Haptoglobins act similar to antibodies. Steps of discovery. Analogous conclusions from pure preparations, umbilical cord sera and animal sera.

The haptoglobins in man and in mammals are agglutinin-like-substances for streptococci having the T4 antigen. The kind of the agglutinin-like behaviour depends on the genetic type of the haptoglobins. Haptoglobins of the types Hp 2-2, Hp 2-2 like and Hp 2-1 are hightitred complete agglutinins (titre in the range between 1:200 up to 1:3000 and higher) whereas haptoglobins of the type Hp 1-1 are "blocking antibodies". - The steps of the discovery and evidence are presented in detail. Different questions dealing with the clinical significance are discussed.