Selective Down-Regulation of T-Cell Receptor Vb6 Gene Expression in Tuberculin Skin Test-Reactive Individuals

             Progression to AIDS occurs more rapidly among tuberculin skin test-reactive HIV-1-infected individuals, who are not treated with anti-TB drugs, suggesting that treatment of latent TB helps to preserve immune function. In this regard, other recent studies, indicating reciprocal enhancement of HIV-1 replication in monocytoid cells co-infected with MTB, are particularly relevant to Hawaii, which ranks first nationally in the incidence of TB. To determine if specific TCR Vb genes are differentially expressed in MTB infection, we employed semiquantitative RT-PCR technique to analyze RNA extracted from unstimulated and PHA-stimulated PBMC obtained from 18 healthy adults (range, 22-55 years), who were either exposed or naive to childhood immunization with bacille Calmette-GuŽrin (BCG) vaccine and either reactive or nonreactive to PPD skin test. Size-fractionated amplified products were visualized by ethidium bromide-staining using the  FOTO/Analystú Image Analysis System (Fotodyne), and the Vb band intensities were compared to the internal Ca control band and quantitated using Collageú version 4.0.  Cells were also analyzed by flow cytometry using monoclonal antibodies against several Vb gene families.  As determined by RT-PCR and flow cytometry, TCR Vb6 was down-regulated in unstimulated and PHA-stimulated PBMC of BCG-exposed and PPD-reactive individuals, when compared to BCG-naive and PPD-nonreactive healthy individuals (P= 0.005, n=6).  These data suggest that the TCR Vb changes may be superantigen-mediated.

Yin, C.Q., Nerurkar, V.R., Kimura, L.H., Dashwood, W-M., and Yanagihara, R.:  Semiquantitative analysis of the T-cell receptor Vb repertoire:  Enhancement of accuracy and reproducibility using a rapid video-imaging system.  Journal of Immunological Methods (in preparation).

Yin, C.Q., Nerurkar, V.R., Kellogg, D.E., Dashwood, W-M., and Yanagihara, R.:  Competitive interference between a widely used Ca primer and Vb gene sequences in the semiquantitative analysis of the T-cell receptor repertoire.  Journal of Immunology (in preparation)  

Yin, C.Q., Nerurkar, V.R., Kimura, L.H., Dashwood, W-M., Kellogg, D.E., and Yanagihara, R.:  Selective down-regulation of T-cell receptor Vb6 gene expression in tuberculin skin test reactive individuals. Immunology (in preparation) .

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