High rate of extrapair paternity in a human population demonstrates diversity in human reproductive strategies

Among nonhuman species, social monogamy is rarely accompanied by complete fidelity. Evolutionary theory predicts that the rate of extrapair paternity (EPP) should vary according to socioecological conditions. In humans, however, geneticists contend that EPP is negligible and relatively invariable. This conclusion is based on a limited set of studies, almost all of which describe European-descent groups. Using a novel, double-blind method designed in collaboration with a community of Himba pastoralists, we find that the rate of EPP in this population is 48%, with 70% of couples having at least one EPP child. Both men and women were very accurate at detecting cases of EPP. These data suggest that the range of variation in EPP across human populations is substantially greater than previously thought. We further show that a high rate of EPP can be accompanied by high paternity confidence, which highlights the importance of disaggregating EPP from the notion of "cuckoldry."

Experimental autoimmune uveoretinitis in the RCS rat: the influence of photoreceptor degeneration on disease expression

S-antigen induced experimental autoimmune uveoretinitis (EAU) was produced in the Royal College of Surgeons (RCS) strain of rat which develops a photoreceptor dystrophy within 2 weeks of birth. Animals were sensitised at 60, 90, and 105 days of age: all animals developed disease, but onset was significantly delayed in older (105 day) animals compared with those aged 60 days at sensitisation (p 0.003). Disease was characterised by the early development of complete serous retinal detachment which resolved in a few days: the prevalence of retinal detachment was increased to 80% in dystrophic animals compared with 10% in the congenic, non-dystrophic controls (p < 0.001). Anterior uveitis was seen in 17/30 control strain eyes, but in none of 30 dystrophic eyes (p < 0.001). Genetically determined photoreceptor and retinal pigment epithelium dysfunction in the RCS rat, which may involve the local accumulation of altered S-antigen, predisposes the dystrophic strain to display an acute retinal detachment in the early stages of EAU. This phenomenon illustrates how biochemical dysfunction of a target organ may influence susceptibility, form, and severity of an experimental autoimmune disease.

Molecular size of retinal vascular leakage determined by FITC-dextran angiography in patients with posterior uveitis

In order to investigate the selective breakdown of the blood-retinal barrier in posterior uveitis angiograms were performed using fluorescein-conjugated dextrans (FITC-dextrans) of different molecular weights (150-kDa, 20-kDa, and 4-kDa) in two healthy controls and six patients with posterior uveitis, and the results compared with those of conventional fluorescein angiography. The smallest FITC-dextran could not penetrate the healthy blood-retinal barrier. Leakage of FITC-dextrans of all sizes was seen from swollen optic discs; dextrans of 4-kDa and 20-kDa leaked from areas of macula oedema; and retinal new vessels allowed the passage of 4-kDa molecules only. These results indicate that there is a differential breakdown of the blood-retinal barrier according to molecular size in various clinical situations associated with posterior uveitis.

Precipitation of experimental autoallergic uveoretinitis by cyclosporin A withdrawal: an experimental model of uveitis relapse

This study set out to determine whether withdrawal of cyclosporin A (CyA) in Lewis rats sensitized to retinal S antigen would precipitate experimental autoallergic uveoretinitis (EAU), and whether challenge of such animals with S antigen or an unrelated stimulus would accelerate EAU onset after drug withdrawal. Rats were sensitized with 50 micrograms S antigen in Freund's complete adjuvant (FCA) and EAU onset was suppressed by 18 days of treatment with CyA at doses ranging from 3 to 10 mg/kg daily. Without challenge, seven out of 11 animals developed EAU with a median onset of 78 days. This was reduced to 68 days in rats challenged on day 32 with FCA alone, to 48 days with 10 micrograms S antigen in FCA, and to 41 days with 50 micrograms S antigen in FCA. The incidence, onset and severity of anterior uveitis and extent of photoreceptor destruction were related to both CyA dose and nature of challenge. The extent of photoreceptor destruction ran parallel with severity of anterior uveitis; and delayed-type hypersensitivity reactivity on day 43 was related to both severity of anterior uveitis (P less than 0.001) and photoreceptor damage (P less than 0.002). At the highest dose, CyA also delayed the appearance of antibody to S antigen; however, subsequent antibody levels were unrelated to EAU severity or to nature of challenge. The results indicate that CyA-induced suppression of the immunological response to S antigen can recover spontaneously after drug withdrawal, that challenge with either S antigen or FCA alone can accelerate the subsequent onset of EAU, and that these phenomena may provide a basis for investigating mechanisms underlying relapse of human uveoretinitis.