TBX21 and pulmonary emphysema: Furthermore, expression of Tbx21, a key transcription factor inducing expression of Ifnγ, was increased in Hhip+/– CD8TTEs compared with age-matched Hhip+/+ cells as early as 15 days of age (Figure 3C), suggesting the activation of the Tbx21-Ifnγ in Hhip+/– CD8TTE cells precedes emphysema and lymphocytic aggregates’ formation in Hhip+/– mice.