Detection of circulating immune complexes with a Raji cell enzyme immunoassay

The primary aim of this work was to produce specific monoclonal antibodies to human growth hormone (hGH) for use in a diagnostic RIA of hGH levels in serum. Three different schedules were used for immunization of BALB/c mice and the splenocytes from each mouse were fused with myeloma cells Sp 2/0 Ag 14. Each fusion resulted in the production of hundreds of hybridomas secreting hGH-directed antibodies. Six antibodies have been fully characterized and have been grouped into pairs which recognize 3 different epitopes on the hGH molecule. One pair exhibits no cross reaction with the structurally related placental hormone, human placental lactogen (hPL), a second pair has low cross reaction with hPL (1.6-3%) and a third pair reacts equally well with hGH and hPL indicating binding to a common epitope in the 2 molecules. The highest affinity antibody, 74/6, which has an affinity constant of 4.4 X 10(10) l/mol and 3% cross-reactivity with hPL, has been used to establish a RIA for serum hGH measurements. Evidence is provided that hGH levels measured in this assay correlate well with those obtained in a conventional rabbit antiserum assay.