Assays for histamine-releasing factors: from identification and cloning to discovery of binding partners.

When using a model to study disease, it may be advantageous to identify molecules responsible for biologic functions observed in the model to better understand the disease process being studied. The late phase reaction is used as a model for chronic inflammation, and the histamine releasing activity observed from late phase fluids was thought to be an important factor in the propagation of symptoms that remain in both the late-phase reaction and in chronic inflammation, when the offending antigen is no longer present. Purification from biologic fluids and identification may be helpful in understanding the role of the histamine-releasing factors in inflammation. Once the specific molecule is identified and cloned, techniques such as yeast two-hybrid screens and co-immunoprecipitation experiments can be used to identify binding partners and further elucidate the role of the cloned molecule. The purification and cloning of human recombinant histamine-releasing factor and the subsequent yeast two-hybrid screen and co-immunoprecipitation will be described to illustrate how any functionally defined molecule can be investigated.