Although severity of lung pathology was greatly reduced by IL-2/anti-IL-2 complex treatment, Mtb numbers in the lung were almost indistinguishable between anti-CD4 treated animals and anti-CD4 + IL-2/anti-IL-2-treated mice at day 140 p.i. These results indicate that despite the failure of IL-2/anti-IL-2 complex treatment to prevent TB reactivation, lung pathology was ameliorated by this treatment regimen. The gene discussed is CD4; the disease is tuberculosis.