Loss of Negative Feedback Control of Nuclear Factor-κB2 Activity in Lymphocytes Leads to Fatal Lung Inflammation

Proteolytic processing of the nuclear factor (NF)-κB2 precursor protein p100 generates the active NF-κB2 subunit p52, which in turn transcriptionally up-regulates p100 expression. p100 also functions as an IκB molecule capable of repressing p52 activity. The biological significance of this negative feedback control loop has yet to be demonstrated in vivo. Here we show that mice deficient in p100 but with constitutive expression of p52 in lymphocytes developed fatal lung inflammation characterized by diffuse alveolar damage with marked peribronchial fibrosis. In contrast, their littermates with only p100 deficiency or constitutive expression of p52 in lymphocytes developed mild lung inflammation with perivascular lymphocyte infiltration and had a normal life span. The fatal lung inflammation is associated with high-level induction of interferon-γ and its inducible inflammatory chemokines, suggesting the involvement of a T-helper-1 immune response. These findings demonstrate the physiological relevance of the NF-κB2 p100 precursor protein in limiting the potentially detrimental effects of constitutive NF-κB2 signaling in lymphocytes.