IL-12Rβ1 chain detected at the cell surface by FACS analysis. PHA-T-cell blasts from a positive control (C+), the patient (P), and a negative control (C-) were stained with various purified mouse monoclonal antibodies (24E6, B101, B103, 12RB44), rat mAb (2B10), or matched isotype control, followed by biotinylated matched Ab and phycoerythrin-conjugated streptavidin. IL-12Rβ1 clone 69310, directly conjugated to R-PE, was compared with a matched conjugated isotype control. Specific signals are represented as plain lines; matched isotype controls are represented as dotted lines.