Cutaneous response to PHA-M and hematological changes in corticosteroid treated cows.

The effect of corticosteroids on the reaction to the intradermal injection of phytohemagglutinin was examined in normal cattle. The associated hematological changes were also examined. Normal, untreated cattle responded to an injection of 1 mg phytohemagglutinin in 0.1 mL saline by a 40 to 80% increase in double skin thickness while corticosteroid treated animals had responses approximately one half of the controls. Neutrophils predominated early in the reaction but were replaced by increasing proportions of lymphoid cells towards 72 hours. These results indicate that an intact and functional inflammatory mechanism is required for a cutaneous response to phytohemagglutinin. Normal animals had a physiological leukocytosis characterized by an increase in mature neutrophils and lymphocytes. Corticosteroid treated animals had a mature neutrophilia, lymphopenia, eosinopenia and monocytosis. These hematological changes were qualitatively similar to those seen in other species.