In vitro immunoglobulin production by peripheral blood lymphocytes from children with acute leukemia under remission-maintenance therapy or off-therapy

As measured by ELISA and analysed by a personal computer

Abstract

In vitro immunoglobulin production by peripheral blood lymphocytes (PBL) from children with acute leukemia (N=41) and their responsiveness to mitogens were evaluated by the Enzyme-Linked Immunosorbent Assay (ELISA), using microtitration plates as a solid-phase immunosorbent. PBL (1×10⁶/ml) were cultured at 37°C for 7 days in a 5% CO₂ incubator in (RPMI 1640) medium supplemented with 10% fetal calf serum, in the absence or presence of mitogen stimulation. As mitogens, pokeweed mitogen (PWM) and Staphylococcus aureus strains Cowan I (SpA Co I) were used. Applying a personal computer, MZ-2000 (SHARP), and model equations, ELISA's standard curves were computed, and Ig concentration in the PBL culture supernatants were calculated from absorbance of the samples measured by ELISA. For analysis ofthe data, patients were divided into two groups: group 1 consisted of those under remissionmaintenance therapy and group 2 those under off-therapy. Under the mitogen-unstimulated condition, IgG production by PBL from children with leukemia (ALL and AML) was, as compared in the mean value, almost equal to that by PBL from control children (N=12). IgA and IgM production, not only in group 1 but also in group 2, were less than the respectivecontrol values. Under the PWM-stimulated condition, amounts of Ig production in group 1 were, in all Ig classes, much less than those in control children. Amounts of Ig production in group 2 were more than those in group 1, but less than those in control children. The responsiveness of PBL to PWM was evaluated by the stimulation index: the index=lg production under PWM-stimulated condition/Ig production under mitogen-unstimulated condition. In allIg classes, the responsiveness to PWM was lower in group 1, but was equal to the controlvalue in group 2. Similar results were obtained with the PBL stimulation by SpA Co I.
Our ELISA can detect small amounts of Ig in PBL culture supernatants. The application of ELISA and a personal computer is useful for the accurate and rapid measurement of Ig in many samples.