Rheumatoid arthritis (RA) is prevalent in Yakima Indians, a Native American tribe. HLA–DR4, the HLA specificity commonly associated with RA in Caucasians, is rare among the Yakima. Using a specific oligonucleotide probe that recognizes DR4 nucleotide sequences associated with RA, a rare HLA–Dw16 gene was identified in 83% of Yakima patients with RA and in 60% of Yakima control subjects. This shared sequence encodes a discrete class II epitope that is highly correlated with RA in both DR4 positive and DR4 negative individuals.

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Although peak exercise capacity (Watts, VO2) during arm exercise is lower in patients with heart failure than healthy subjects, when expressed as a percentage of peak leg capacity, the extent of the exercise intolerance they experience during arm exercise does not differ from healthy subjects.