Endogenous superantigens: tools for dissecting T-cell repertoire selection

Host Genetic Determinants of Vaccine-Induced Eosinophilia During Respiratory Syncytial Virus Infection

In BALB/c mice, sensitization with the attachment protein (G) of respiratory syncytial virus (RSV) leads to CD4+ T cell-mediated lung eosinophilia during subsequent challenge with RSV. To determine the host genetic influences on this model of lung eosinophilia, we tested 15 different inbred mouse strains. Eosinophilia developed in all H-2d (BALB/c, DBA/2n, and B10.D2), but not in H-2k (CBA/Ca, CBA/J, C3H, BALB.K, or B10.BR) mouse strains. Among H-2b mice, 129 and BALB.B developed eosinophilia, whereas C57BL/6 and C57BL/10 did not. Testing first generation crosses between sensitive and resistant strains showed that eosinophilia developed in all H-2dxk (n = 5), irrespective of background genes, but not in H-2dxb (n = 2) mice. In vivo depletion of CD8+ T cells or IFN-γ rendered C57BL/6, but not BALB.K mice, susceptible to eosinophilia. Analysis of B10 recombinant mice showed that the Dd allele (in B10.A(5R) mice) prevented CD8+ T cell accumulation in the lung, resulting in intense lung eosinophilia. However, the Db allele (in B10.A(2R) and B10.A(4R) mice) supported CD8+ T cell expansion and prevented eosinophilia. Intracellular cytokine staining showed that lung eosinophilia correlated with reduced IFN-γ and increased IL-10 expression in lung T cells. These results are compatible with the unifying model that Th2 cells mediate the disease but can be inhibited by CD8+ T cells secreting IFN-γ. Our findings have important implications for the development of protective, nonpathogenic vaccines for RSV disease.

A truncated T cell receptor repertoire reveals underlying immunogenicity of an antigenic determinant

Induction of T cell responses to an antigenic peptide that is known to bind a major histocompatibility complex molecule is a function of either the T cell receptor (TCR) repertoire or regulatory influences by CD8 or CD4 regulatory T cells. We have tested the hypothesis that a lack of 10 TCR V beta gene segments in V beta a mice may result in an incomplete repertoire of regulatory T cells involved in maintaining peripheral tolerance. Such a hole in the repertoire of regulatory cells could result in expression of T cell responses to antigenic determinants that normally remain undetected in mice with a wild-type repertoire of TCR V beta gene segments. We show here that H-2d mice respond to the peptide 74-96 of hen egg-white lysozyme (HEL) when they are of V beta a haplotype at their TCR locus. The wild-type (V beta b) H-2d mice with their complete set of 20 TCR V beta gene segments fail to respond to HEL 74-96. The 74-96-specific T cell responsiveness was revealed in the wild-type (V beta b) mice when they were treated in vivo with anti-CD8 antibody, implicating the existence of regulatory cells that prevent expression of T cell responses specific for peptide 74-96. This is a demonstration that holes in the regulatory T cell repertoire can, in certain circumstances, become beneficial to the host, for example, in susceptibility against pathogens.