The concept of immune surveillance (in the context of malignant
transformation) was developed in the early sixties and seems to have
remained the major conceptual framework for tumor immunology.
It poses the existence of a circulating pool of competent immune cells
which readily recognize and destroy encountered transformed cells before a
tumor emerges. The transformation of normal cells into tumor cells may
very well be a frequent phenomenon but the immune system usually eliminates
these degenerate cells immediately. If a tumor does arise, this would be
due to a failure of the immune system to either recognize or destroy the
tumor cells.
Although numerous attemps have been made to provide experimental evidence
for this idea, I have the impression that no or very few convincing
confirmatory reports have been produced.
In contrast, it has become increasingly clear that spontaneously arising
(human) tumors are not or very poorly immunogenic (which is not surprising
since they are host cells). The immune system may therefore not be failing
but is simply not capable/conceived to recognize transformed cells.
Yet, a large deal of the current cancer research focusses on the
immune system and why it fails or which mechanisms a tumor cell may have
developed to escape immune surveillance.
I therefore wonder:
i) do I miss something (references ?) when believing that there is no
concrete evidence for the immune surveillance concept ?
ii) if not, how comes that everyone focusses on this fallacy instead of
concentrating on more relevant aspects of tumor biology ?
For all adepts of the immune surveillance idea:
don't shoot me but convince me !
Els Torreele
Cellular Immunology
Free University Brussels
e-mail: etorreel at vub.ac.be
