DISAPPEARANCE OF CD4 ANTIGEN IN A CASE OF ADULT T CELL LEUKAEMIA

Adult T cell leukaemia (ATL) cells usually have a mature helperlinducer T cell phenotype tCD3*. CD4'. CD5'. CD8 1 (Yamada. 198 3 : Yamada c! d. 1989). Hoirever. some cases with poor prognoses have unusual phenotypes, like doublepositive (CD4' CD8-) . double-negative (CD.1CD8). and a defect of the CD5 antigen (Yaniada u t d. 1985). More interestingly. the surface phenotypes determined at the initial diagnosis sometimes change upon relapse or when the illness is exacerbated t Yamada r t ti!. 1984). The gain of CD8 and the loss of CD5 have been observed. However. clonal analysis of ATI, cells by surveying human 7' cell leukaemia virus tvpe I (IITLV-I) integration sites. or by examining T cell receptor {TCR) gene rearrangemrnt profiles. before and after change has not been done. Therefore. there remains a possibility that the apparent change of surface phenotype is actually due to the expansion of a minor ATL cell population which may have been present at the time of the initial diagnosis. This report describes an ATL patient whose leukaemic cells have changed from ClMCDX to double-negative (CD4CD81. Clonal analysis by surveying HTLV1 integration sites confirmed that the double-negative cells were truly derived from CD.1CD8ATL cells. A 59-year-old woman, who had had chronic ATL for 2 years. was admitted to our hospital because of a worsened skin eruption. Blood counts were: a WBC of 7.4 x 10y/l (ATL cells 26%): a haemoglobin level of 12.5 g/dl; and platelets were 107 x 1 Oy/l. Surface marker analysis showed the CD2+ T cells constituted 98.3% of the total, CD4+ T cells were h O ~ 3 0 / , . and CDX' T cells were 204% (Fig 1) on admission, suggesting that her ATL cells were of CD4+ CD8T cell origin. She was treated with two courses of extracorporeal photochemotherapy. which improved the skin condition and decreased the number of ATL cells. This effect was, however, transient and the number of ATL cells increased rapidly and their reactivity to a n t i 0 4 3 antibody decreased. At this point. chemotherapy was initiated. The effects of chemotherapy were also transient, and the patient died of pneumonia 4 months after admission. The proportion of CD4+ T cells had decreased further to 7.4%. suggesting that the ATL cellsurface phenotype had changed to double-negative.