Purification and biochemical characteristics of two distinct human interleukins 1 from the myelomonocytic THP-1 cell line

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Abstract
An effective induction protocol for the production of interleukin 1 (IL 1) by human myelomonocytic cell line (THP-1) cells was developed, and two biochemically distinct human IL 1 peptides were purified. Lipopolysaccharide, silica and hydroxyurea by themselves did not induce IL 1 production, but these three stimulants in combination had a synergistic effect on the production of IL 1 by THP-1 cells. A 17-kilodalton (kDa) form of human IL 1 with a pI of 7.0 (IL 1-.beta.) was purified to homogeneity by sequential chromatography on DEAE-Sephacel, Sephacryl S-200, CM high-performance liquid chromatography (HPLC), and hydroxyapatite HPLC. The recovery of IL 1-.beta. activity was 45%, and the specific activity was 2.3 .times. 107 units/mg. Both IL 1-.beta. and a second 17-kDa IL 1 moiety with a pI of 5.0 (IL 1-.alpha.) were also extracted from stimulated THP-1 cells and purified to homogeneity by sequential chromatography on Sephacryl S-200, ion exchange HPLC, and hydroxyapatite HPLC. The recovery of IL 1-.beta. from cell extracts was 5.6%, and the specific activity was 3 .times. 107 units/mg. In contrast, only 0.85% of IL 1-.alpha. was recovered with a specific activity of 5.3 .times. 107 units/mg. The amino acid sequence of the amino-terminal end and amino acid composition of purified IL 1-.beta. obtained from both culture supernatants and cell extracts of THP-1 cells showed complete identity with those of IL 1-.beta. from culture supernatants of normal human monocytes, suggesting that normal human monocytes and THP-1 cells produce identical intracellular human IL 1-.beta. and release the same activity into the culture supernatant. The amino composition of IL 1-.alpha. in cells extracts of THP-1 cells was noticeably different from that of IL-.beta. but closely resembled the predicted amino acid composition of the 17-kDa C-terminal portion deduced from the published cDNA nucleotide sequence of IL 1-.alpha., further supporting the existence of two distinct human IL 1 genes. In conclusion, the purification and biochemical characterization of two distant human IL 1 moieties (IL 1-.alpha. and IL 1-.beta.) from a human myelomonocytic cell line establish that this leukemic cell line produces two distinct IL 1 moieties that are biologically and biochemically identical with the products of normal human monocytes. Consequently, THP-1 cells provide a good source of IL 1 that is identical with that produced by normal human monocytes.