Differential expression of Mtv loci in MHC class II-positive thymic stromal cells.
Despite the important role played by endogenous superantigen in shaping the T cell repertoire, little is known concerning the expression of the different Mtv loci in cells of the thymic microenvironment involved in repertoire selection. Here we have examined the expression of a panel of Mtv Ags by different MHC class II+ stromal cel types using reverse transcriptase-PCR and monitored the effects of these stromal cells on the development of cells expressing Mtv-reactive TCR V beta elements in closed thymic organ culture systems. Although Mtv-6 and Mtv-8/9 mRNAs are expressed in normal thymus lobe organ cultures, no Mtv expression was detected in MHC class II+ thymic epithelial cells. In contrast a striking pattern of differential expression was observed in dendritic cells of thymic origin that were devoid of Mtv-8/9 but expressed readily detectable levels of Mtv-6. This pattern of Mtv gene expression correlated well with TCR V beta repertoire development. TCRV beta 3+ T cells, normally deleted in response to Mtv-6, were virtually absent from the single positive thymocyte compartment in thymic organ cultures where dendritic cells are present but were present in reaggregate cultures where the only MHC class II-positive cells were thymic epithelial cells. On the other hand, V beta 11+ T-cells were not deleted in organ cultures, possibly reflecting the absence of Mtv-8/9 expression in dendritic cells. Our studies suggest that the influence Mtvs have on shaping the T cell repertoire not only depends on their expression within a particular strain but also on their tissue specific expression in relation to MHC class II, which is necessary for their presentation.
Moore
N C
NC
Center for Clinical Research in Immunology and Signalling, Medical School, University of Birmingham, United Kingdom.
Anderson
G
G
McLoughlin
D E
DE
Owen
J J
JJ
Jenkinson
E J
EJ
D000818:Animals; D002874:Chromosome Mapping; D017637:Clonal Deletion; D000949:Histocompatibility Antigens Class II / Q000032:analysis*; D051379:Mice; D008807:Mice, Inbred BALB C; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000032:analysis; D017154:Stromal Cells / Q000276:immunology; D018089:Superantigens / Q000235:genetics* / Q000502:physiology; D013950:Thymus Gland / Q000166:cytology* / Q000276:immunology
D000949:Histocompatibility Antigens Class II; D016693:Receptors, Antigen, T-Cell, alpha-beta; D018089:Superantigens