The role of hyperemia in cellular hypersensitivity reactions

The three physiological processes vascular permeability, blood flow and lymphocyte migration were all enhanced in tuberculin reactions induced in guinea pigs and sheep and also in normal lymphocyte transfer reactions in sheep. Microspheres labelled with 85Sr were used to measure blood flow to dermal sites and it was found that cellular hypersensitivity reactions had blood flows 7-25 times that of normal skin at the reaction peak. Vascular permeability was measured as an increase in the flow rate of afferent lymph or, in guinea pigs, as the enhanced leakage of intravascular 125I-albumin. When the permeability-inducing peptide bradykinin was injected directly into tuberculin reaction, the resulting permeability was greater than the sum of the tuberculin and bradykinin permeability taken individually and it was concluded that the hyperemia enhanced the permeability-inducing capacity of bradykinin. When the traffic of lymphocytes through hypersensitivity lesions was measured in sheep by cannulating the regional afferent lymph vessels and continuously collecting the lymph, the increase in lymphocyte traffic was of the same order of magnitude as the increase in blood flow. It is suggested than the antigen-induced enhancement of blood flow caused the increase in lymphocyte traffic and that the mechanism was similar to that occurring within lymph nodes during the immune response to all antigens.