TUBERCULIN-INDUCED DELAYED-TYPE HYPERSENSITIVITY REACTION IN A MODEL OF HU-PBMC-SCID MICE GRAFTED WITH AUTOLOGOUS SKIN

We have developed an animal model to study human delayed-type hypersen sitivity reactions. Previous studies in humans have shown after tuberc ulin injection the presence of a mononuclear cell infiltration, with a lmost no eosinophils, associated with a preferential Th-l-type cytokin e profile. Human skin graft obtained from tuberculin-reactive donors w as grafted onto the back of severe combined immunodeficient mice. Afte r healing, mice were reconstituted intraperitoneally with peripheral m ononuclear cells. Tuberculin and diluent were injected intradermally, and skin biopsies were performed 72 hours later. Skin grafts were divi ded into two parts, one for immunohistochemistry and one for in situ h ybridization studies. Immunohistochemistry was performed on cryostat s ections using the alkaline phosphatase anti-alkaline phosphatase techn ique. In the tuberculin-injected sites as compared with the diluent-in jected sites, there were significant increases in the number of CD45() pan leukocytes and CD4(+) CD8(+), CD45RO(+) T cells but not in CD68( +) monocytes/macrophages and EG2 or MBP+ eosinophils. The activation m arkers CD25 and HLA-DR were up-regulated in the tuberculin-injected si tes. In situ hybridization was performed using S-35-labeled riboprobes for interleukin (IL)-2, interferon (IFN)-gamma, IL-4, and IL-5, After tuberculin injection, a preferential Th-l-type cytokine profile was o bserved with significant increases in the numbers of IL-2 and IFN-gamm a mRNA-expressing cells. These results are similar to those reported a fter tuberculin-induced delayed-type hypersensitivity in humans, sugge sting that this model might be useful to study cutaneous inflammatory reactions.