The quantum model of T-cell activation: Revisiting immune response theories

Anti-tumor immunity relies on targeting tissue homeostasis through monocyte-driven responses rather than direct tumor cytotoxicity

Background

Metabolic dysfunction-associated fatty liver disease (MAFLD) can progress to hepatocellular carcinoma (HCC), yet the immune mechanisms driving this transition remain unclear.

Methods

In a chronic Western diet (WD) mouse model, we performed single-nuclei RNA sequencing to track MAFLD progression into HCC and subsequent tumor inhibition upon dietary correction.

Results

Carcinogenesis begins during MAFLD, with tumor cells entering dormancy when HCC is mitigated. Rather than purely tolerogenic, the liver actively engages immune responses targeting myofibroblasts, fibroblasts and hepatocytes to maintain tissue homeostasis. Cytotoxic cells contribute to turnover of liver cells but do not primarily target the tumor. NKT cells predominate under chronic WD, while monocytes join them in HCC progression on a WD. Upon dietary correction, monocyte-driven immunity confers protection against HCC through targeting tissue homeostatic pathways and antioxidant mechanisms. Crucially, liver tissue response-not merely immune activation-dictates whether tumors grow or regress, emphasizing the importance of restoring liver tissue integrity. Also, protection against HCC is linked to a distinct immunological pattern, differing from healthy controls, underscoring the need for immune reprogramming.

Conclusion

These findings reveal the dual roles of similar pathways, where immune patterns targeting different cells shape distinct outcomes. Restoring tissue homeostasis and regeneration creates a tumor-hostile microenvironment, whereas tumor-directed approaches fail to remodel the TME. This underscores the need for tissue remodeling strategies in cancer prevention and treatment.

On the nature of signal 1 delivered to lymphocytes: A critical response to some considerations put forward in support of the quantum model of T cell activation

The original Two Signal Model of lymphocyte activation stated that antigen-dependent lymphocyte cooperation is required for lymphocyte activation, whereas a single or a few antigen-specific lymphocytes can be inactivated by antigen. A virtue of this model is its ability to account for peripheral tolerance. Both the activation and inactivation of lymphocytes were envisaged to require the lymphocytes' antigen-specific receptors to interact with antigen, leading to signal 1. We consider here the proposition that the sensitivity to antigen concentration for the generation of signal 1, to support both differentiation processes, is the same. This situation optimizes the reliability of peripheral tolerance and minimizes the effects of lymphocyte inactivation in decreasing the diversity of the lymphocytes. We consider the broader implications of this Principle of Parsimonious Sensitivity in regulating the activity of lymphocytes.