Effect of locally administered heparins on delayed-type hypersensitivity reactions

Inflammatory reactions involved in delayed-type hypersensitivity (DTH) are associated with extravascular coagulation and fibrin deposition. Heparin and other anticoagulants administered systemically inhibit DTH reactions but the direct effect of intradermally injected heparin on the development of DTH skin responses has not been reported. The effects of heparin on the DTH reaction elicited by ovalbumin (OVA) in guinea pigs 1-3 weeks after sensitization were examined. Unfractionated heparin, low affinity heparin (LAH; non-anticoagulant) and high affinity heparin (HAH; anticoagulant) were injected together with suboptimal amounts of OVA. Heparin and LAH enhanced skin induration, LAH (0.5 micrograms) by an average of 50% above that due to OVA alone at 24 h (p less than 0.01). In contrast, HAH (0.5 micrograms) significantly reduced skin induration at 24 h. Heparin and LAH also significantly increased cellular infiltration with LAH having the greater effect. At 4 h the infiltrate consisted mainly of neutrophils whereas at 24 h mononuclear cells predominated. Fibrin deposition, assessed both by immunohistology and quantitation of radioactive fibrin extracted from skin test sites, was increased by 30% when OVA was tested in the presence of LAH. Mast cell heparin released locally at sites of DTH has the potential to modulate these reactions in either a pro- or anti-inflammatory manner. This study is the first to demonstrate differences in the capacities of LAH and HAH to modulate cell-mediated inflammation.