The human interferon system: characterization and classification after discovery of novel members.

The human interferon (IFN) system is the best characterized of all animal IFN systems. Until recently it is thought that all IFNs and IFN-related genes and proteins have been discovered. However, in the last three years, the discovery and characterization of IFNs including IFN-epsilon (IFN-epsilon), IFN-kappa (IFN-kappa) and a novel IFN-lambda (IFN-lambda) family, in particular, substantially changed this opinion. In this article, we attempt to review recent developments in the field of interferon discovery and present an overview of current classification of the human IFN system. Characterization of the constituent parts of the human IFN system including ligands, receptors and players involved in the signal transduction pathway are discussed.

Priming with interferon-alpha 1 or interferon-alpha 2 enhances the production of both subtypes simultaneously.

A short period of incubation with interferon-alpha ("priming") increases the amounts of IFN-alpha formed by human peripheral blood leukocytes when subsequently induced with a virus. We investigated specifically the effect of priming on the production of two individual subtypes, IFN-alpha 1 and IFN-alpha 2. The rate of interferon synthesis and the amounts formed were equally potentiated in leukocytes primed with either IFN-alpha 1 or IFN-alpha 2. Whichever of these was used for priming had no selective effect on the relative increased production of IFN-alpha 1 or IFN-alpha 2.

Increased sensitivity of an enzyme immunoassay for human interferon alpha 1 using a mixture of three monoclonal antibodies.

A sensitive sandwich ELISA for the quantification of human interferon (IFN)-alpha 1 was designed. The assay employed IFN-alpha 1- specific polyclonal antibody for coating and monoclonal antibodies (mAbs) to IFN-alpha 1 as a second antibody. A major increase in sensitivity of the assay could be achieved, when polyclonal antibody was combined with a mixture of three mAbs binding to different regions of IFN-alpha 1, compared to the combination of a polyclonal antibody with a single mAb. The sensitivity of the established ELISA was close to that of an antiviral IFN-bioassay. The ELISA did not cross-react with IFN-alpha 2, beta, tau or omega. The immunoassay allowed to estimate the content of IFN-alpha 1 in leukocyte IFN-alpha to about 25-50% or to 2-6% in Namalwa IFN-alpha, respectively.

Comparison of antigenic properties of three interferon (IFN)-alpha 2 subvariants and establishement of a quantitative IFN-alpha 2 ELISA.

Three subvariants of human IFN-alpha 2 (2a, 2b, 2c) were found antigenically highly homologous, using a panel of specific monoclonal antibodies (MoAbs) directed to seven epitopes. Only in the region 30-41 IFN-alpha 2c showed some difference from the corresponding structures of subvariants 2a and 2b. An universal sandwich ELISA for the quantification of all subvariants of human IFN-alpha 2 was designed. A major increase in sensitivity of the immunoassay could be achieved, when polyclonal antibody to IFN-alpha 2 was combined with a mixture of three MoAbs to distinct sites of IFN-alpha 2, compared to the combination of a polyclonal antibody with a single MoAb. The sensitivity of the established ELISA ranged between 1-10 units/ml of IFN-alpha 2 and no cross-reactivity with IFN-alpha 1, -beta, or -omega 1 could be observed. We estimated the content of IFN-alpha 2 to about 56% in leukocyte IFN-alpha or to about 72% in Namalwa IFN-alpha.

Porcine leukocyte interferon exhibits close antigenic relatedness to human interferon alpha 2, but not to human interferon alpha 1.

As reported by others using polyclonal antisera, natural human and porcine interferons (IFN)-alpha are antigenically related. Using monoclonal antibodies (mAb) in neutralization and ELISA experiments, we found differences in the subtype/antigenic composition between virus-induced porcine and human leukocyte preparations. Human leukocyte IFN-alpha contains two major antigenically distinct subtypes, IFN-alpha 1 and IFN-alpha 2. However, swine leukocytes produced only a single predominant species of IFN-alpha with high antigenic homology to human IFN-alpha 2. Moreover, we were unable to detect close antigenic relatedness between recombinant porcine and human IFN-alpha 1 subtypes.