EXPRESSION OF CD8-BETA AND ALTERATION OF CELL-SURFACE PHENOTYPE IN ADULT T-CELL LEUKEMIA-CELLS

Typical adult T-cell leukaemia (ATL) cells have a CD4(+)CD8(-) cell su rface phenotype, but atypical phenotypes such as CD4(+)CD8(+) and CD4( -)CD8(+) have also been reported. The CD8 molecule is composed of alph a and beta chains and commonly used monoclonal antibodies against CD8 molecule detect only CD8 alpha. Since it has been reported that CD8 al pha can be induced in mature CD4(+) T cells by cell activation, but no t CD8 beta, we studied whether ATL cells which express CD8 alpha may a lso express CD8 beta. We found some cases of CD8 alpha(+) ATL were als o positive for CD8 beta. Furthermore, we experienced a case whose ATL cell surface phenotype changed from CD4(+)CD8 alpha(+)CD8 beta(+) to C D4(-)CD8 alpha(+)CD8 beta(+) and finally to CD4(+)CD8 alpha(-)CD8 beta (-). Southern blot analysis revealed that the monoclonal integration o f human T lymphotropic virus type I (HTLV-I) was identical throughout the course of the study, indicating that a single clone had demonstrat ed the alterations, These data suggest that peripheral CD4(+)CD8(+) AT L cells can express not only CD8 alpha, but also CD8 beta and that a s ingle ATL cell clone has the potential to change its surface phenotype in vivo as well as in vitro.