XXXX , @entity1138 , and @entity1880 as regulatory agents of MHC class II-associated invariant chain expression.

@entity1 @entity19 @entity1880 @entity1138 @entity379
The @entity19 and @entity1 major histocompatibility complex class II-associated invariant chain genes are expressed in mature B cells and in antigen-presenting cells. Several pre-B cell lines and fibroblasts do not naturally contain invariant chain mRNA. Expression is inducible, however, by interferons and other agents interfering with proliferation. @entity1138 induces the transcription of the gene in pre-B cells, but not in fibroblasts. @entity379 acts in both types of cells. @entity1880 inhibits the induction of the invariant chain mRNA by @entity379 , suggesting that protein synthesis is required. In fact, @entity1880 itself increases the transcriptional rate at the invariant chain gene, suggesting the existence of a labile repressor or an indirect action through @entity1880 arrest of the cell cycle. Lipopolysaccharide (LPS) activation of B lymphocytes causes a rapid decrease of the invariant chain mRNA level and of the amount of invariant chain protein due to rapid turnover. Also class II alpha and beta mRNA expression decreases after LPS treatment. The decrease of invariant chain protein is accompanied by increased surface expression of alpha and beta. The @entity19 invariant chain gene transfected into @entity1 fibroblasts is regulated by the same agents and the same dose of agents as is the endogenous gene. The differentiation marker invariant chain thus seems to be transcribed from a gene that is accessible to regulation even in nonlymphoid cells and the expression of which is linked to states of nonproliferation. The sequence responsible for these responses is contained within the cloned genomic fragment and is conserved between @entity19 and @entity1 .
