concanavalin-a and Hyperemia

Popliteal and prefemoral lymphatics of sheep were cannulated, and lymph was collected before and during the course of responses to PPD and concanavalin A. Hyperemia-inducing activity (HIA) and phospholipase A2 (PLA2) were released into lymph in response to antigenic stimulation, whereas lymph plasma draining unstimulated lymph nodes had consistently little or no detectable HIA and PLA2 activity. HIA appeared in the lymph efferent to the stimulated node at a time when blood flow to the responding node was enhanced. While the appearance of HIA did not directly correlate with changes in lymphocyte output, lymph protein concentration, or lymph flow rates, there was, however, a statistically significant correlation between HIA and PLA2 levels in lymph plasma, suggesting that extracellular PLA2 may contribute to the vasoactivity in lymph and thereby modulate blood flow to areas of antigenic stimulation. Vasoactive lymph, injected into rabbits, induced hyperemia via an indomethacin-sensitive pathway, since the induction of hyperemia was abrogated by pretreatment of injection sites with indomethacin. The extracellular release of PLA2 in response to inflammatory stimuli may represent an amplification mechanism for the generation of high levels of prostaglandins found in lymph draining stimulated nodes.

Topics: Animals; Blood Circulation; Capillary Permeability; Concanavalin A; Female; Hyperemia; Hypersensitivity, Delayed; Indomethacin; Lymph; Lymph Nodes; Phospholipases; Phospholipases A; Phospholipases A2; Rabbits; Regional Blood Flow; Sheep; Time Factors

A nonlymphokine mediator of hyperemia has been shown to be secreted by both rabbit peritoneal exudate cells stimulated with 5% glycogen and by concanavalin A treated cells from afferent lymph of sheep. This mediator is not stored in an active form in cells, but is either activated or synthesized de novo in response to antigenic or mitogenic stimuli. Secretion of the mediator is inhibited by culturing cells in the presence of dexamethasone but not indomethacin. However, expression of the activity is inhibited by pretreatment of the assay animals with indomethacin, suggesting a two-step induction of hyperemia. A similar mediator was found to be secreted by sheep and rabbit alveolar lavage cells, and rat peritoneal exudate cells. The presence of this hyperemia-inducing activity from diverse species suggests a fundamental role in controlling blood flow. Alteration of blood flow may modulate delivery of blood-borne cells and factors to sites of chronic inflammation.

Topics: Animals; Cells, Cultured; Concanavalin A; Culture Media; Dexamethasone; Female; Glycogen; Guinea Pigs; Hyperemia; Indomethacin; Inflammation; Injections, Intradermal; Kinetics; Lung; Mice; Mitogens; Phagocytes; Rabbits; Rats; Sheep; Sonication; Therapeutic Irrigation; Time Factors