Tissue mosaics and clonal mechanisms of atherogenesis.

It is known that atherosclerotic lesions arising in aortae of females heterozygous for the A and B variants of glucose-6-phosphate dehydrogenase are frequently though not invariably of one enzyme type. The occurrence of heterotypic lesions rules out single-cell origin. However, it is possible to analyze the results of such studies in terms of multicellular atherogenic foci. The variance in enzyme proportions in the normal tissue mosaic permits an assessment of clump or patch size. Then an application of geometrical probability permits the derivation of a relation between the proportion of monotypic lesions and the size and cell number of the original atherogenic focus. Comparison with suitable experimental data gives reasonable estimates of these cell numbers. The influence of selection in the cell population on such estimates is considered.