TH17 cells induce severe pathologic skin and pulmonary lesions. TH17 cells (5 × 10⁶; n = 6), whole splenic T cells (5 × 10⁶; n = 4), or CD4⁺/CD25⁻ (5 × 10⁶; n = 5) cells were transferred with T cell–depleted bone marrow cells into lethally irradiated B6D2 recipients. At day 14 after transplantation organs were harvested and processed as described in “Methods.” Histopathologic assessment of the skin (A), lung (B), liver (C), colon (D), and spleen (E) was performed by one author (A.P.-M.) who was blinded to the identity of the transplanted mice. Values presented are the mean plus or minus SEM for each group. Score range for each tissue, 0-4. Representative pictures of skin from animals receiving TH17 cells (F), total T cells (G), or CD4⁺/CD25⁻ cells (H). → denotes epidermal hyperplasia, ▿ denotes follicular obliteration. Representative pictures of lung from animals receiving TH17 cells (I), total T cells (J), or CD4⁺/CD25⁻ cells (K). → denotes perivascular cuffing and vasculitis, ▿ denotes peribronchiolar cuffing, ★ denotes area of alveolar hemorrhage. TT = total T cells, CD4 = CD4⁺/CD25⁻ cells. Original magnification: skin = ×200, lung = ×100.