Abstract
Molecular and cellular assessment of dermal delayed-type hypersensitivity (DTH) responses is a useful approach for evaluating the mechanism of action (MOA) of immunomodulatory agents. In the present report, we characterized the delayed-type hypersensitivity response induced by keyhole limpet hemocyanin (KLH), and validated its utility by evaluating an immunomodulator, BIRB-796. Intradermal KLH challenge of the ear pinna following subcutaneous antigen sensitization resulted in a pronounced skin inflammation that peaked at 24-48h. At the molecular level, there was an activation of 3 mitogen-activated protein kinases (MAPKs: p38, JNK and ERK), an induction of the chemokines CCL2/JE, CXCL2/Mip-2, CXCL1/KC, CCL3/Mip-1alpha CCL4/Mip-1beta and CXCL10/IP-10, and expression of the cytokines IL-1beta and IL-10 in the ear parenchyma. Modulation of TNFalpha protein level was only detected in ex-vivo ear whole organ cultures (EWOC). Consistent with this inflammatory profile there was an infiltration of neutrophils and mononuclear cells into the ear parenchyma. BIRB-796, a potent allosteric p38 MAPK inhibitor attenuated the ear swelling response, which correlated with a reduced inflammatory profile. BIRB-796 inhibited p38 but not JNK or ERK kinase activation, decreased multiple chemokines which correlated with a decrease in the infiltration of neutrophils and macrophages; CD4 T cells were modesty reduced. Similarly, there was a decrease of levels of cytokines including IL-1beta, IL-10 and TNFalpha. These data support the utility of this model for evaluating immunomodulators on skin inflammation and suggest that modulation of p38 kinase may be of therapeutic value for the treatment of inflammatory skin conditions.