Abstract
Most cases of adult T-cell leukemia (ATL) are thought to result from vertical transmission, with few clear-cut cases linked to horizontal transmission. We analyzed the percentage of flower-like cells, which included both flower cells (ATL cells morphologically) and abnormal lymphocytes, per 400 lymphocytes in carriers and noncarriers alike, and postulated that this percentage might be a risk factor for ATL in HTLV-I carriers. Accordingly, we analyzed for (1) any difference in the percentage of flower-like cellsbetween symptomless carriers of HTLV-I and noncarriers ; (2) any difference in the incidence of flower-like cells between the vertical and sexual transmission groups of pregnant women who were positive for HTLV-I ; and (3) any difference in the incidence of flower-like cells between pregnant women and their mothers who were positive for HTLV-I. The percentage of flower-like cells in the symptomless carriers was significantly higher than that in the noncarriers. The mean percentage of flower-like cells in the symptomless carriers was between one and two percent and was stable, unaffected by generation or by transmission route. Even though the flower-like cells are most likely transformed by HTLV-I, the percentage of flower-like cells does not appear to be a risk factor for ATL. It is not known why so few cases of ATL developed in our sexual transmission group, which had the same percentage of flower-like cells as did the vertical transmission group.
