RESUMO
Gut-associated lymphoid tissues (GALTs) interact with intestinal microflora to drive GALT development and diversify the primary antibody repertoire; however, the molecular mechanisms that link these events remain elusive. Alicia rabbits provide an excellent model to investigate the relationship between GALT, intestinal microflora, and modulation of the antibody repertoire. Most B cells in neonatal Alicia rabbits express V(H)n allotype immunoglobulin (Ig)M. Within weeks, the number of V(H)n B cells decreases, whereas V(H)a allotype B cells increase in number and become predominant. We hypothesized that the repertoire shift from V(H)n to V(H)a B cells results from interactions between GALT and intestinal microflora. To test this hypothesis, we surgically removed organized GALT from newborn Alicia pups and ligated the appendix to sequester it from intestinal microflora. Flow cytometry and nucleotide sequence analyses revealed that the V(H)n to V(H)a repertoire shift did not occur, demonstrating the requirement for interactions between GALT and intestinal microflora in the selective expansion of V(H)a B cells. By comparing amino acid sequences of V(H)n and V(H)a Ig, we identified a putative V(H) ligand binding site for a bacterial or endogenous B cell superantigen. We propose that interaction of such a superantigen with V(H)a B cells results in their selective expansion.
Assuntos
Linfócitos B/imunologia , Alótipos de Imunoglobulina/metabolismo , Switching de Imunoglobulina/genética , Imunoglobulina M/metabolismo , Região Variável de Imunoglobulina/genética , Tecido Linfoide/imunologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Sítios de Ligação , Cálcio/metabolismo , Clonagem Molecular , DNA Complementar/genética , Citometria de Fluxo , Imunofluorescência , Genes de Imunoglobulinas/genética , Alótipos de Imunoglobulina/imunologia , Switching de Imunoglobulina/imunologia , Imunoglobulina M/imunologia , Região Variável de Imunoglobulina/biossíntese , Tecido Linfoide/microbiologia , Modelos Moleculares , Dados de Sequência Molecular , Coelhos , Análise de Sequência de DNA , Superantígenos/genéticaRESUMO
The transcriptional activity of human immunodeficiency virus type 1 (HIV-1) is affected by many cellular factors. Homologies near the HIV-1 initiator region to the DNA-binding sequences of YY1, a multifunctional transcription factor known to regulate diverse viral and cellular promoters, suggested that YY1 might regulate HIV-1. Antibody to YY1 blocked the formation of complexes by HeLa cell nuclear extract and a DNA oligonucleotide encoding the HIV-1 initiator region. HIV-1 long terminal repeat (LTR) expression, as measured the expression of a transfected LTR-CAT reporter gene, was repressed more than 12-fold by the cotransfection of a YY1 expression vector. HIV-1 production by both COS-1 and CEM cells after transfection of an infectious molecular HIV-1 clone was repressed 7- to 20-fold by cotransfection of a YY1 expression vector. HIV-1 production was also decreased threefold in a CD4-positive lymphocyte cell line chronically infected with HIV-1 (8E5) after transfection of YY1. In situ hybridization studies confirmed that YY1 reduced HIV-1 RNA expression. YY1 may play an important role in the regulation of HIV-1 LTR expression in vivo and virus production by infected cells.