8. Either (1) a negative PPD test using 5 T.U. intradermal testing per CDC guidelines and no evidence of active TB by history on chest X-ray at the time of enrollment or (2) a positive PPD with no evidence of active TB on chest X-ray at the time of enrollment and either past or present treatment with adequate therapy for at least one month prior to first dose of study medication. Full prophylaxis regimens will be completed. Subjects who have been BCG-vaccinated will also be skin-tested.