Assay for Soluble IL-2R in Serum
Measurement of serum concentrations of soluble IL-2R was performed by using commercially available Celfree Interleukin-2 Receptor Bead Kit (T Cell Sciences Inc, Cambridge, MA). This assay system is a two-site, solid-phase enzyme immunometric assay which employs two noncompeting monoclonal antibodies to the human IL-2Ra chain. Briefly, each 50 jjlL of serum sample was incubated with a plastic bead coated with a monoclonal antibody directed against one epitope on the IL-2R molecule, and with a horseradish peroxidase-conjugated monoclonal antibody directed against a second epitope on the same molecule, for 90 min at room temperature. buy antibiotics online
Following the incubation, unbound conjugate was removed by washing and the bead was incubated with o-phenyl-enediamine solution for 30 min at r<x)m temperature. By using a Dynatech MR700 Microelisa reader (Dinertech Laboratories Inc, Chantilly, VA) set at 492 nm, the absorbance of each sample was measured. Since the amount of serum IL-2R present is directly proportional to the absorbance of the sample, the concentration of soluble IL-2R was calculated by comparing it to already known standards containing IL-2R. The minimum detectable concentration of IL-2R was 50 U/ml. Its normal range (the mean value ±2 SD) was determined by measuring the concentrations in 97 healthy control subjects (52 men, 19 to 63 years old, and 45 women, 21 to 43 years old).