Sandwich enzyme immunoassay for murine IL-3

A reproducible, sensitive immunoassay for murine interleukin-3 (IL-3) has been developed using two preparations of polyclonal antipeptide antibodies. Rabbits were immunized with the N-terminal peptide 1–29 (IL-3) coupled to KLH and the antibodies were affinity purified on immobilized peptide 1–29 (IL-3). This antibody preparation showed good reactivity with native IL-3, and was used to coat polyvinyl microtiter trays. IL-3 captured by this first antibody was detected by the addition of anti-IL-3 serum (second antibody) raised in sheep against synthetic full length IL-3 (1–140). This test reliably detects IL-3 from every source tested (T cells, WEHI-3B cells, recombinant material from transfected COS 7 cells or murine myeloid FDC-P1 cells transfected with an IL-3 containing retrovirus) with a sensitivity to 2 to 4 U/ml of bioactive IL-3 or about 60 pg synthetic IL-3/ml. The test is performed within 5 to 6 h compared to 2 to 3 d of a standard bioassay.