Ontogeny of Xenopus NK cells in the absence of MHC class I antigens.

This paper explores the ontogeny of NK cells in control and early-thymectomized (Tx) Xenopus laevis through phenotypic analysis of cells expressing the NK cell antigen 1F8 and by performing in vitro cytotoxic assays. Dual color flow cytometry reveals that a few 1F8positive splenocytes first emerge in late larval life, at approximately 7-weeks post-fertilization. This is about 2-weeks after the time when surface MHC class Ia expression can first be detected.

Identification and characterization of Xenopus CD8+ T cells expressing an NK cell-associated molecule.

Growing evidence suggests that some immune responses are mediated not only by conventional and distinct NK cells and CTL, but also by T cell subsets expressing NK receptors and NK cell-associated molecules. Consistent with our previously published finding that the mAb 1F8 identifies non-T/non-B cells in Xenopus that effect NK-like killing in vitro, we now report that in vivo treatment with this mAb impairs rejection of transplanted MHC class I-negative tumor cells. However, we also find that the NK cell-associated molecule recognized by mAb 1F8 is expressed by a minor population of CD8+ T cells, in which fully rearranged TCRbeta mRNA of at least three different V families can be identified, by contrast, 1F8+/CD8- (NK) cells lack such TCRbeta message.

Minor histocompatibility antigen-specific MHC-restricted CD8 T cell responses elicited by heat shock proteins.

In mammals, the heat shock proteins (HSP) gp96 and hsp70 elicit potent specific MHC class I-restricted CD8(+) T cell (CTL) response to exogenous peptides they chaperone. We show in this study that in the adult frog Xenopus, a species whose common ancestors with mammals date back 300 million years, both hsp70 and gp96 generate an adaptive specific cellular immune response against chaperoned minor histocompatibility antigenic peptides that effects an accelerated rejection of minor histocompatibility-locus disparate skin grafts in vivo and an MHC-specific CD8(+) cytotoxic T cell response in vitro. In naturally class I-deficient but immunocompetent Xenopus larvae, gp96 also generates an antitumor immune response that is independent of chaperoned peptides (i.