Effects of methylprednisolone on concanavalin A-induced human lymphocyte blastogenesis: a comparative analysis by flow cytometry, volume determination and 3H-thymidine incorporation

The inhibition of concanavalin A-induced human peripheral blood lymphocyte blastogenesis by methylprednisolone (MP) was studied by using flow cytometry and tritiated thymidine (3H-TdR) incorporation. Flow cytometric determinations of volume, low angle forward light scatter, and nucleic acid showed MP to be a potent inhibitor of blastogenesis. The effects were concentration-dependent and correlated with 3H-TdR uptake. By using the single cell analytic capability of flow cytometry, the target stages of the cell cycle where MP affects lymphocyte activation were determined. Evidence is presented that steroids can block both early and late phases of this process.