Solid phase enzyme immunoassay of human interleukin 2 utilizing antibodies against synthetic IL-2 peptides

In the present study, solid phase enzyme immunoassay utilizing antibodies against synthetic IL-2 peptides was used for quantitative measurements of human recombinant and lymphoid IL-2 preparations. The 27-peptide MCF-III-6 (Leu-Glu-His-Leu-Leu-Leu-Asp-Leu-Gln-Met-Ile-Leu-Asn-Gly-Ile-Asn-Asn-- Tyr-Lys-Asn-Pro-Lys-Leu-Thr-Arg-Met-Leu) that comprises the region 14-40 from the IL-2 amino acid sequence was synthesized and used for immunization of rabbits. Resulting anti-MCF-III-6 polyvalent rabbit antibodies reacted specifically in EIA up to dilution of 10(-7) with the MCF-III-6 peptide used for immunization as well as with 16-peptide I-16 (Cys-Nle-Gly-Ile-Asn-Asn-Tyr-Lys-Asn-Pro-Lys-Leu-Thr-Arg-Met-Leu) that comprises the region 27-40 from the IL-2 amino acid sequence. The anti-MCF-III-6 antibody reacted also with human recombinant IL-2 preparations obtained from three producers (Cetus, Riga and Amersham), to the concentration of 0.1 ng/ml, and with various human lymphoid IL-2 preparations. Direct correlation was observed between quantitative measurements of human lymphoid IL-2 by EIA and by CTLL bioassay. It can be concluded that utilization of synthetic IL-2 peptides provides a suitable and comparatively unexpensive immunogen for the production of IL-2 antibodies and that the solid phase EIA using such antibodies can be employed as a rapid, reproducible, and sensitive method for quantitative examination of both recombinant and lymphoid IL-2 preparations.