Response to Prednisolone of Cultured Immunoglobulin-producing Human Lymphoid Cells

The survival of asynchronously growing lymphoid cells (T₁ cells) in vitro decreased to 50% viability after 1 hr treatment with concentrations of prednisolone above 10 µg/ml. Treatment with prednisolone for 24 hr produced a decrease in cell survival to a plateau of 30% viability for concentrations above 10 µg/ml. After 48 hr treatment, 10 µ/ml prednisolone reduced viability to 12%. Synchronously growing T₁ cells were least sensitive to prednisolone treatment (50 µg/ml) during S phase (DNA synthesis period) and most sensitive during G₁ (pre-DNA-synthesis period). This cell cycle specificity is postulated to be an explanation for the presence of prednisolone-resistant cells in asynchronously growing populations. Immunofluorescence studies on the effect of prednisolone (100 µg/ml) on immunoglobulin production indicated there was no correlation between the length of drug treatment and reduction in the percentage of immunoglobulin-producing cells. These results suggest that the mechanism of prednisolone-induced immunosuppression in lymphoid cells is primarily lymphopenia.