Clinical immunology
Different sensitivity of resting and activated blood lymphocytes and B leukemic lymphoblasts on dexamethasone action

The aim of the study was to assess the influence of dexamethasone on these cellular parameters that turn of the cells on apoptosis process. Evaluation of intracellular pH, changes in cell cycle phases and annexin-V staining were performed. The study include peripheral blood lymphocytes isolated from 25 healthy volunteers non stimulated or stimulated with PHA or SAC to blastogenesis and 10 samples of children’ bone marrow taken at the day of BpC-ALL diagnosis. The cells were cultured in medium with or without dexamethasone (10-6M). Analysis of pHi, cell cycle and apoptosis test were performed on flow cytometer Coulter EPICS-XL.

Acidification of lymphocytes and lymphoblasts incubated with dexamethasone was seen in 10-25% percentage of cells. Rest of cells showed alkalization. Lymphocytes had lower pHi than lymphoblasts, also after incubation with dexamethasone. Dexamethasone influenced phase S in cell cycle only in T lymphocytes (72 h), while it had no effect on B lymphocytes and lymphoblasts. The evaluation subG1 phase showed significant influence of dexamethasone on lymphocytes T and lower on lymphocytes B. Dexamethasone had also significant influence on lymphocytes T stimulated with PHA. There was no influence on lymphocytes B stimulated with SAC and lymphoblasts. After 2 and 48 h of incubation with dexamethasone there was a significant increase in percentage of lymphocytes in early apoptotic phase. Influence of dexamethasone on apoptosis of lymphoblasts was lower.

Presented results indicate that dexamethasone is not very potent inductor of B-lymphoblasts apoptosis.