Spontaneous regressions and remissions from cancer are still regarded as a mystery. But a careful analysis of case studies reveals that many, if not a majority, of cases have a close connection in time with a hefty feverish infection. This observation, which was published 2001, can be well aligned with early cancer treatments by Busch, Coley and co-workers more than 100 years ago, and with epidemiological data collected and discussed recently (2005 , 2008a , 2008b).
Meanwhile, a biochemical explanation for all these links is available. Pathogenic substances collectively termed 'pathogen recognition receptor ligands' (PRRL) most likely are responsible. A subgroup of PRRL are PAMP-substances. These substances act on the innate immune system and enable an enhanced immune reaction compared to antigen alone.
While the focus in cancer immunotherapy has been on antigen alone, i.e. the adaptive immune system, attention is shifting very recently towards the involvement of the innate system. Several PRRL are presently in diverse clinical trials. However, the way these drugs are applied in cancer immunotherapy might need revision (see Hobohm, Grange, Stanford "PAMP in cancer immunotherapy", Critical Reviews in Immunology 28(2):95–107). Correctly - in a metronomic fashion - applied, it is conceivable that PRRL have unleveraged potential in cancer immune therapy, as first preliminary experiments in mice and human patient case studies have shown (see references).