Interferons are species-specific proteins, which induce antiviral and antiproliferative responses in animal cells. They are a major defense against viral infections and abnormal growths (neoplasms). Interferons are produced in response to penetration of animal cells by viral (or synthetic) nucleic acid and then leave the infected cell to confer resistance on other cells of the organism. In contrast to antibodies, interferons are not virus specific but host specific. Thus, viral infections of human cells are inhibited only by human interferon. The human genome contains 14 nonallelic and 9 allelic genes of -interferon (macrophage interferon), as well as a single gene for -interferon (fibroblast interferon). Genes for any two or more variants of interferon, which have originated from the same wild-type gene are called allelic genes and will occupy the same chromosomal location (locus). Variants originating from different standard genes are termed non allelic. - and - interferons are...