Analysis of T-cell defects in the specific immune response against acute lymphoblastic leukemia cells

We previously showed that a specific antileukemia T-cytotoxic response is s pontaneously elicited in acute lymphoblastic leukemia (ALL) patients and mi ght contribute to host antileukemia defense, even though it is insufficient for tumor growth control. In this study, we report that multifactorial fac tors account for some of the acquired immune defects seen in ALL patients. In bone marrow of ALL patients, T cells do not express CD40L and CD25 marke rs, their apoptosis rate is increased, and a predominance of a CD4 cell sub set expressing a Th2 phenotype is detected. A lack of expression of B7-1 mo lecules and other activation molecules is observed on all ALL blasts. These different parameters combined lead to in vivo dysfunction of T-cell prolif erative and cytotoxic activity. (C) 1999 International Society for Experime ntal Hematology. Published by Elsevier Science Inc.