Expression and Temperature-Dependent Regulation of the Beta2-Microglobulin (Cyca-B2m) Gene in a Cold-Blooded Vertebrate, the Common Carp (Cyprinus carpio L.)

摘要

Expression of beta2-microglobulin (β 2m) in the common carp was studied using a polyclonal antibody raised against a recombinant protein obtained from eukaryotic expression of the Cyca-B2m gene. β 2m is expressed on peripheral blood Ig+ and Ig- lymphocytes, but not onerythrocytes and thrombocytes. In spleen and pronephros, dull- and bright-positive populationscould be identified correlating with the presence of erythrocytes, thrombocytes, and matureleucocytes or immature and mature cells from the lympho-myeloid lineage, respectively.Thymocytes were shown to be comprised of a single bright-positive population. The Cyca-B2mpolyclonal antiserum was used in conjunction with a similarly produced polyclonal antiserum toan MHC class I (Cyca-UA) α chain to investigate the expression of class I molecules onperipheral blood leucocytes (PBL) at different permissive temperatures. At 12℃, a temporarydownregulation of class I molecules was demonstrated, which recovered to normal levels within3 days. However, at 6℃, a lasting absence of class I cell-surface expression was observed, whichcould be restored slowly by transfer to 12C. The expression of immunoglobulin molecules onB cells was unaffected by temperature changes. The absence of the class cell-surface expressionwas shown to be the result of a lack of sufficient Cyca-B2m gene transcription, although Cyca-UA mRNA was present at comparable levels at all temperatures. This suggests that class Iexpression is regulated by a temperature-sensitive transcription of the Cyca-B2m gene.