Leukocytes and Tissue Factors in the Pathogenesis of Bovine Mastitis

Abstract

SUMMARY Inoculation of histamine in doses of 5 mg. or more into bovine mammary glands produced swelling and firmness within 10 to 30 minutes. The reaction progressed rapidly to maximum within a few hours and then subsided to become almost imperceptible by the next day. The marked increase in the vascular permeability led to highly increased concentrations of serum albumin in whey, but leukocytosis into the milk did not develop. A mild reaction was seen when 1 mg. of histamine was given, and smaller doses did not elicit measurable reactions. Serotonin (maximal dose of 100 mg.) produced only slight edema which lasted for a few hours and marked tenderness of the gland during the day of inoculation. There was no leakage of serum albumin nor increase of leukocytes into the milk. Bradykinin produced neither palpable nor measurable signs of inflammation. Neutrophil leukocytes were isolated from mastitic milk from glands inoculated with small amounts of Escherichia coli endotoxin at the preceding milking. Washed intact leukocytes, disrupted leukocytes, and crude lysosomal preparations from such leukocytes were inoculated in normal lactating mammary glands of normal cows. All produced signs of acute inflammation in the udder, viz., swelling and firmness of the gland, increased concentrations of blood serum albumin in the whey, and diapedesis of neutrophil leukocytes from blood to milk. The palpable signs of inflammation usually subsided within 24 hours, but leukocytosis into the milk usually continued for 3 to 5 days. The response seemed to be influenced by the number of leukocytes inoculated and varied with the lysosomal preparations.