Occurrence of IgG fragments in the urine of the newborn calf

The observation that newborn calves develop a proteinuria reaching a maximum between 25 and 30 hours of life after feeding colostrum was confirmed. Among the proteins precipitable at 3.6 M ammonium sulfate, two components with IgG specificity but differing in electrophoretic mobility have been found. Antisera were produced in rabbits against Fab or Fc fragments derived from colostral IgGs by papain digestion. Using these antisera, a urinary Fab was demonstrated to be antigenically identical to the papain Fab. In contrast, the urinary Fc was found to be at least in part antigenically deficient with respect to the papain Fc. With the aid of an immunoadsorbent, the antigen binding activity of the urinary Fab could be demonstrated in calves after the ingestion of colostrum which contained antibody. The site where the degradation of IgGs occurs could not be elucidated.