Individual lymphocyte subset composition determines cAMP response to isoproterenol in mononuclear cell preparations from peripheral blood

Abstract

The aim of the present study was to examine to what extent isoproterenol-stimulated cAMP production in mononuclear cells, isolated from resting human subjects, was correlated with lymphocyte subset composition. Peripheral blood was collected from 14 healthy male subjects, who rested in the sitting position. Mononuclear cells were prepared by density centrifugation and subset composition was determined by two-colour flow cytometry. Cyclic AMP production was determined by a radioimmunoassay after inhibition of phosphodiesterase and stimulation with isoproterenol. NK-cells (CD3-CD56+) were positively correlated to total cAMP concentrations (basal cAMP plus increase in cAMP). T_cytotoxic cells (CD8+) were positively correlated to the relative increase in cAMP. T_helper cells (CD4+) were negatively correlated to total cAMP concentrations and B-lymphocytes (CD(19 + 20) +) were negatively correlated to the relative increase in cAMP. The results support the view that NK-cells and T_cytotoxic cells have higher β₂-adrenoceptor densities and more receptors with high affinity than T_helper and B-cells. In conclusion, our study demonstrates that cAMP levels in blood mononuclear cells obtained from normal subjects show substantial variation. This variation is at least in part due to differences in lymphocyte subset composition in the same subjects. Therefore, it is important to know the lymphocyte subset composition when evaluating cAMP accumulation in mononuclear cell preparations from peripheral blood.

Key Words:

• β-adrenoceptors
• cAMP
• isoproterenol
• lymphocytes
• lymphocyte subpopulations