spread), themaintenanceof chronic elements present in the local environment
(most of the time, these chronic elements are normal self components of the
organism, but chronically present tumor constituents can also lead to active
maintenance of the tumor by the immune system, which progressively sees
these elements as normal) (Pradeu et al. 2013; Pauken and Wherry 2015), and
the repairof the local tissue (in physiological conditions, this repair is
a necessary process insuring the integrity of the tissue, but in the context of
cancer repair mechanisms can favor cancer progression).
The crucial point here is that decohesion as seen in cancer can concern all
these different activities, not just elimination: the immune system, which in
most cases prevents cancer progression by elimination, containment, mainte-
nance, and repair, can in some circumstances promote cancer progression
because of deregulated elimination, containment, maintenance, and/or repair.
Moreover, all these activities must be understood diachronically: they do not all
intervene at the same time, and the immune system can switch from one effect to
the other (for example, it can initiate the destruction of abnormal components
and later contribute to their maintenance because they have become chronically
expressed in the tissue).
Does the immune system dysfunction when it promotes cancer progression
via a deficit in elimination or containment and/or via maintenance processes
and/or via repair processes? I suggest distinguishing two situations here. The
Immune SystemEliminates
abnormal cellsFigure 4.2 The traditional view of immune-mediated cohesion, as proposed
by the immunological surveillance hypothesis. According to this view, the
immune system directly eliminates abnormal cells, such as cancer cells (in red)
in the tumor. (Figure drawn by Wiebke Bretting).
Philosophy of Immunology 39