The major myelin protein genes are expressed in the human thymus

Demyelinating diseases, such as multiple sclerosis (MS) in man or experimental allergic encephalomyelitis (EAE) in rodents, may include an associated immune response directed against myelin protein antigens such as the proteolipid protein (PLP) and the myelin basic protein (MBP). Development of an immune response has been attributed, in part, to the sequestration of central nervous system antigens behind the blood-brain barrier. Recently, we identified a novel gene, the golli gene, which overlaps the mbp gene. The Golli transcription unit produces a family of mRNAs, and their corresponding proteins possess MBP epitopes known to be encephalitogenic in EAE. Transcription of the golli gene was detected in immune system tissue. Therefore, we wished to determine whether genes that encode the two major myelin protein components, PLP and MBP, were expressed in the human thymus. Our data demonstrate that both the plp and golli genes are transcribed in the fetal human thymus. Moreover, both the PLP and DM-20 transcripts are produced from the plp gene, and the HOG 7 and HOG 5 transcripts are produced from the golli gene. Confocal fluorescent immunohistochemistry using antibodies for the PLP/DM-20 and Golli proteins, co-localized expression of these antigens to thymic macrophages. Thus, the plp and golli genes are expressed, and their corresponding protein produced, in an antigen presenting cell in the human immune system.