delayed hypersensitivity was measured by skin testing with four common recall antigens , and serum immunosuppressive activity was determined by the ability of the patient 's serum in 10 % concentration to suppress by 50 % or more the phytohemagglutinin ( pha ) stimulation of normal human lymphocytes as compared to pooled normal serum .
C0003320
antigens
C0024262
stimulation