Development and α₁-mediated inhibition of DSS-induced colitis is independent of lymphocytes. Immunodeficient Rag2^–/– mice were fed DSS over 7 days and treated with mAb (control or anti-α₁) every second day starting at day 0. Disease severity was measured daily and is expressed in terms of (a) body weight, (b) fecal blood, (c) diarrhea, and (d) disease activity index (combined index of a + b + c). The isotype mAb-treated group exhibited an exaggerated course and severity of colitis compared with WT mice receiving either DSS alone or with the isotype-matched mAb (compare with Figure 1 and Figure 2). *P < 0.05, anti-α₁ mAb vs. isotype mAb. Data represent mean ± SEM.