Document Type



The frequency of Australia antigen (Au) in Malaita (using the immunodiffusion (ID) method) is higher than in any Pacific population studied with the exception of Utirik Island, in the Marshall Islands. The frequency is among the highest recorded for any non-hospitalized human population. The frequency of Au (by ID) is higher in younger people (with the exception of the very young) and in general higher in males than in females. The male to female sex ratio decreases with age. This confirms previous observations. The frequencies of Au in Lau and Baegu are higher than in Kwaio. The possibility of transmission by mosquitoes and/or infected shellfish is discussed. A suggestion is made that infected shellfish may contribute to the high frequency of Au in the Lau people. The frequency of Au is higher in Malaita than in Bougainville. This also conforms reasonably well to the Austronesian, non-Austronesian linguistic division. It is hypothesized that this linguistic division may serve as a marker of biological differences for this trait as it appears to for others. The differences in frequency between the Austronesian and non-Austronesian groups could be accounted for mainly by a higher frequency of Au in the younger Austronesians. It is suggested that some of this difference could be due to differences in the frequencies of Au subtypes in the two populations, and to age differences in the distribution of subtypes. Radioimmunoassay (RIA), complement fixation (CF) and ID methods are compared for sensitivity; RIA is the most sensitive and ID the least. Data are presented which support the view that RIA and CF are measuring the same antigenic material as the ID method. There is a very high frequency of anticomplementary (AC) activity in the Lau population. This increases with age. A hypothesis is made that AC accurately reflects at least in part an increasing frequency of Au complexes with age. This may account for the decrease with age of persistent Au (as measured by ID).