Tuberculosis (TB) in children is not only more likely to cause more severe disease than that seen in adults, it is also more likely to be extrapulmonary. Moreover, pediatric TB is very difficult to diagnose and suffers from a lack of understanding of host
biomarkers for monitoring the progression of disease. Hence, we sought to identify the expression patterns of a variety of
biomarkers in the plasma of children with pulmonary TB (PTB) and extrapulmonary TB (ETB), as well as in healthy control (HC) children. Thus, we examined a variety of circulating markers reflecting tissue
inflammation, oxidative stress, innate immune activation,
fibrosis, and the
cytokine response. Children with active TB, compared to HC children, showed markedly elevated plasma levels of
matrix metalloproteinases and their endogenous inhibitors. In addition, children with active TB had significantly elevated levels of
C-reactive protein, α-2 macroglobulin, and
haptoglobin, as well as hemoxygenase 1. Markers of innate immune activation (
lipopolysaccharide [LPS] and
lipopolysaccharide-binding protein [LBP]) were significantly lower in ETB than in PTB children. Although there were no significant differences between the two groups in their levels of
cytokines (type 1 [
gamma interferon (IFN-γ),
tumor necrosis factor α (TNF-α),
interleukin 2 (IL-2), and
IL-12], type 2 [IL-4, IL-5,
IL-13, and IL-33], and most type 17 [IL-17A, IL-22, IL-1β, and IL-6] and type 1
interferons [IFN-α and IFN-β]) or most of the
cytokines associated with immune modulation (IL-10 and IL-20), pediatric TB was associated with elevated plasma
transforming growth factor β (TGF-β),
IL-21, and
IL-23 levels. Thus, pediatric TB is characterized by elevated levels of a variety of
biomarkers at homeostasis, suggesting that these responses may play a crucial role in disease pathogenesis.