The small intestine (SI) of vertebrates exhibits low tumorigenesis and rarely supports metastatic growth from distant tumors. Many theories have been proposed to address this phenomenon, but none has been consistently supported. One candidate mechanism is that the vast immunologic compartment of the SI provides a heightened level of tumor immunosurveillance. Consistent with this, we have identified a molecule of low abundance from bovine SI that has the hallmarks of a potent immunostimulant and may be associated with the natural suppression of cancer in the intestinal tract. The protein originates from an endemic gut protozoan, Eimeria spp., and is homologous to the antigen 3‐1E previously isolated from the avian apicomplexan E. acervulina. We show here that it is a very potent stimulator of IL‐12 release from dendritic cells, upregulates inflammatory modulators in vivo (IL‐12, MCP‐1, IL‐6, TNF‐α and INF‐γ) and has antitumor properties in mice. In addition, it is synergistic in vitro with anti‐CD40 antibody, IFN‐γ, IL‐4 and GM‐CSF; is active across species barriers in vivo; and has no observable toxicity. Based on these activities, we speculate that it is an inducer of protozoan‐targeted innate immunity, which may explain its potential benefit to the intestinal tract and potency as an agent in cancer immunotherapy.

An understanding of the cosmic ray modulation of life processes is critical to space exploration, evolution and current medical science. Previous evidence has implicated a role for cosmic rays in US female cancer, involving a possible cross-generational foetal effect. This study explores the global nature of that effect by examining cancer time variations for population cohorts in five countries on three continents. Age–period–cohort analysis was used to separate cohort-related effects from period-related effects, generating time signatures for comparisons among both male and female populations in the United States (US), United Kingdom (UK), Australia (AU), Canada (CA) and New Zealand (NZ). The available cancer mortality data spanned most of the 20th century for US, UK and AU, with shorter periods for CA and NZ. The longest cohort series spanned 1825 to 1965 and exhibited two peaks of higher mortality likelihood approximately 75 years apart in all countries and in both sexes. The constancy of this oscillation on three continents and both hemispheres suggests the presence of a global environmental effect. To explore a possible source for this effect, the birth cohort oscillation is shown to correlate with the variations in background cosmic radiation one generation prior to the birth cohorts. This confirms an earlier study correlating human breast cancer mortality and galactic cosmic rays. A corroborating correlation is also noted between the latitude dependences of cancer incidence in 42 countries and the intensity of background cosmic rays. The role of germ cells as a possible target of this radiation is discussed, emphasizing the amplification that must occur to make this weak radiation relevant to human health. Germ cell timing for this effect has profound implications for evolution, long-distance space travel and the colonization of planets with high background radiation.