Hypothesis: The differential tuberculosis reactivation rates observed between monoclonal anti-TNF antibodies (infliximab, adalimumab) and the soluble TNF receptor (etanercept) are primarily driven by complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) targeting membrane-bound TNF-α on granuloma macrophages, rather than simple TNF-α neutralization.

Background: Keane et al. (NEJM 2001) documented 70 TB cases with infliximab, predominantly extrapulmonary/disseminated. Subsequent meta-analyses (Solovic et al., ERJ 2010) confirmed 4-40x higher TB reactivation with monoclonal TNFi vs 2-4x with etanercept. Both drug classes neutralize soluble TNF-α, yet their TB risk profiles diverge markedly.

Mechanism: Monoclonal antibodies bind membrane-bound TNF-α (mTNF) on macrophages within M. tuberculosis granulomas, triggering CDC and ADCC. This induces macrophage apoptosis within the granuloma wall, compromising structural containment of dormant bacilli. Etanercept preferentially neutralizes soluble TNF-α with lower mTNF affinity, preserving granuloma integrity.

Testable prediction: In a humanized mouse model of latent TB granulomas, infliximab will cause greater granuloma disruption (measured by macrophage viability, C3d/C5b-9 deposition, bacterial CFU release) compared to etanercept at equivalent TNF-α neutralizing doses.

References: Keane NEJM 2001;345:1098. Solovic ERJ 2010;36:1185. Tracey Pharmacol Ther 2008;117:244. Wallis J Infect Dis 2008;197:S31.