Researchers from the University of Paraná in Curitiba, Brazil, characterized the prevalence of autoantibodies among the indigenous Indian population and collated their findings with demographic and clinical data.
The team analyzed serum samples from 256 people from the Kaingang and Guarani tribes living in the Mangueirinha Reservation in southern Brazil, along with 65 Mestizos (mixed-race) and 180 non-Indians. Participants who tested positive for rheumatoid factor (RF) or antinuclear antibodies (ANA) were evaluated clinically for rheumatoid arthritis (RA).
Writing in the journal Rheumatology International, João Luiz Coelho Ribas and colleagues report that RF was detected in 10.30% of Kaingang Indians, 2.04% of Guarani, 3.08% of Mestizos, and 3.33% of non-Indians.
Interestingly, women from the Kaingang tribe had the highest prevalence of RF, at 14.0%, and all Kaingang individuals with a confirmed clinical diagnosis of RA were female.
The prevalence of ANA seropositivity did not differ among the four groups, however.
The authors remark that a higher incidence of RA in women versus men has already been reported in other Amerindian tribes, and is thought to reflect hormonal factors that are involved in disease initiation and progression.
By contrast, the differences in prevalence between the Kaingang and Guarani Indians could be related to genetic differences, as genetic factors are known to be actively involved in the pathogenesis of RA.
“Serologic studies with clinical-laboratorial association are of importance and it is necessary to screen individuals at risk for autoimmune disease, such as Indian populations,” Ribas et al conclude.
“Our data corroborate previous findings emphasizing the high prevalence of autoantibodies and autoimmune disease among Amerindian populations, and reinforces the role of genetic, age, and hormonal factors in their development.”