Abstract
Anaphylactic shock of a protracted nature can be regularly elicited in guinea pigs actively sensitized to various antigens and challenged via the subcutaneous route. During the protracted shock when tests are made for Arthus reactions the response is absent or scant. For example, animals sensitized to both sheep erythrocytes and ovalbumin were injected with sheep cells subcutaneously and ovalbumin intracutaneously. Four hours after the onset of the resultant shock, there were minor or no Arthus reactions to ovalbumin. Similar results were obtained in mice sensitized to both egg albumin and hemocyanin. Sensitized controls given only the local injection of antigen showed strong Arthus reactions. Possible mechanisms for the inhibition of local hypersensitivity reactions by systemic antigen-antibody reactions were discussed.