Of various swine serum fractions tested, the only one that reacted with pancreas extracts contained gamma, beta and alpha-globulins. In the absence of alpha-globulin, precipitation reactions were not observed.

Sera of newborn SPF piglets, containing 50% alpha-2 globulin, formed more intense precipitation lines with swine pancreas extracts than were formed by the sera of their dams with the same extracts.

The pancreas-reacting activity of swine sera was completely removed by absorption with pancreatic tissue. This property was not removed by absorption with guinea pig kidney, or beef, swine or human erythrocytes.

Maceration of pancreatic tissue released reactive substances in a polydispersed form. This was demonstrated by the ability of almost all supernates and sediments from differential centrifugation of such preparations to form precipitation lines with swine sera. Reactive substances from swine pancreas were found to be relatively heat labile, being inactivated in one hour at 56C.

No evidence was obtained in this study to indicate that the observed precipitation reactions were related to hog cholera virus and its corresponding antibody. The reactions are believed to have resulted from the interaction of protein-related substances present in normal swine pancreas with a relatively heat stable component, possibly alpha-globulin, in swine serum.