In line with previous studies on viral infections (Schijns et al, 1998; Oxenius et al, 1999; Krueger et al, 2021), neutralization of IL-12 did not significantly alter CD4+ T cell differentiation (Appendix Fig. S5A–D), prompting us to explore the influence of another cytokine known for reinforcing TH1 identity through positive feedback loops, IFN-γ (Wakil et al, 1998; Lighvani et al, 2001; Schulz et al, 2009). Here, IFNG is linked to viral infectious disease.