Antibodies against Phosphorylcholine among New Guineans Compared to Swedes: An Aspect of the Hygiene/Missing Old Friends Hypothesis

Background: We here study antibodies against phosphorylcholine (anti-PC) which we reported to be inversely associated with atherosclerosis, cardiovascular disease (CVD), and autoimmune conditions. In previous studies, we determined that this inverse association is more pronounced at low levels with high risk and at high levels, with decreased risk. We compare individuals from Kitava, New Guinea (with low risk of these conditions), with Swedish controls. Methods: We studied a group of 178 individuals from Kitava (age 20-86), and compared those above age 40 (n = 108) with a group of age-and sex-matched individuals from a population based cohort in Sweden (n = 108). Traditional risk factors for CVD and fatty acids were determined. IgM, IgG, and IgA anti-PC were tested by enzyme-linked immunosorbent assay (ELISA). Results: All anti-PC measures were significantly lower among Swedish controls as compared to Kitavans (p < 0.001), independent of traditional risk factors. Having low levels of anti-PC, defined as below 25th percentile of values among Swedish controls, was associated with this cohort after adjustment for other risk factors (OR 5.7, 95% CI 2.2-14.7 for IgM; OR 31.7, 95% CI 3.9-252 for IgA; and OR 11.1, 95% CI 2.4-51 for IgG). Conclusions: PC is highly exposed on microorganisms and helminths (common on Kitava) exposing much PC which humans and hominids may have been exposed to for millions of years. We propose that low anti-PC levels in the developed world could be a new aspect of the hygiene hypothesis, generating a pro-inflammatory and pro-atherosclerotic state.