Beschreibung:
<jats:p>The role of nonthymic epithelial (non-TE) MHC in T cell repertoire selection remains controversial. To analyze the relative roles of thymic epithelial (TE) and non-TE MHC in T cell repertoire selection, we have generated tetraparental aggregation chimeras (B6-nude↔BALB/c and B6↔BALB/c-nude) harboring T and B cells from both parents, whereas TE cells originated exclusively from the non-nude donor. These chimeras mounted protective virus-specific TE and non-TE MHC-restricted T cell responses. To further evaluate whether non-TE MHC alone was sufficient to generate a functional T cell repertoire, we generated tetraparental aggregation chimeras lacking MHC class II (B6-nude↔MHCII<jats:sup>−/−</jats:sup>) or both MHC molecules (B6-nude↔MHCI<jats:sup>−/−</jats:sup>II<jats:sup>−/−</jats:sup>) on TE cells, but not on cells of B6-nude origin. Chimeras with MHC-deficient TE cells mounted functional virus-specific CD8<jats:sup>+</jats:sup>but not CD4<jats:sup>+</jats:sup>T cell responses. Thus, maturation of functional CD4<jats:sup>+</jats:sup>T cell responses required MHC class II on thymic epithelium, whereas CD8<jats:sup>+</jats:sup>T cells matured in the absence of TE MHC.</jats:p>