Natural cytotoxicity towards allogeneic tumour targets in Xenopus mediated by diverse splenocyte populations

Xenopus NK cells identified by novel monoclonal antibodies

“…The 1F8-enriched cells were 90 % pure and over half the enriched population expressed AM22-defined CD8. Mean CD8 fluorescence intensity of 1F8 + cells was 8 5 (defined as CD8 lo ), in contrast to the approximately fourfold higher fluorescence intensity seen on T cells (CD8 hi ) stained with AM22 ( [17,18]; unpublished data with siblings of animals used here). In a second experiment (Fig.…”

“…Cells were cultured in growth factor-rich medium (GFM) derived from ConA-stimulated splenocytes ( [17] and Sect. 4.3].…”

“…Recent studies [15][16][17][18] on control and earlythymectomized (Tx) Xenopus frogs have identified candidate NK cells that display lymphokine-activated natural cytotoxicity towards the MHC-deficient B 3 B 7 lymphoid tumor cell line [19,20]. Since Tx Xenopus frogs are permanently deficient in identifiable T cells and display greatly reduced expression of TCR g transcripts and loss of detectable T cell function [18], they have been used here to generate and screen three mAb that identify and characterize NK-like cells in Xenopus spleen, liver and intestine.…”

Tolerance Induction in Thymectomized, Adult Xenopus by Co-Transplantation of Thymus and Tolerated Skin Graft

“…From these observations, we conclude that the tol-JB skin grafts contain several types of cell populations derived from the primary host (JJ larvae transplanted with JB skin grafts that were tolerated for 4-5 weeks): 1) cells which suppress the JB skin-graft rejection (Ono and Tochinai, 1995); 2) cells which are primed to destroy JB skin grafts; and 3) other immunoreactive cells such as passenger antigen presenting cells (APCs). NK-like cells, which were reported to develop in the spleens of E-Txd adults but were absent from the spleens of E-Txd larvae (Horton et al, 1998), may also have played a role when skin grafts were transplanted to ETxd adults. At present, however, we cannot directly examine the contribution of these cell populations in tolerance induction due to the lack of appropriate cellular markers in Xenopus.…”

“…Several lines of evidence suggest that adults have "stronger" immunoreactivities than larvae. For example, the larval antibody repertoire is smaller than that of adults (Hsu and Du Pasquier, 1992); most of the adult-type MHC class I positive cells do not appear until larvae reach st. 57 (Flajnik et al, 1986;Flajnik and Du Pasquier, 1988); and cells with an NK-like activity develop in the spleens of E-Txd adults but are absent from the spleens of E-Txd larvae (Horton et al, 1998). Furthermore, it is possible that the immunoreactivity of thymectomized (both E-Txd and L-Txd) adults, even those reconstituted with a thymus, is lower than that of nonthymectomized adults at the time of tol-JB skin transplantation, because it takes a few days for the transplanted thymus to become vascularized (Horton, 1997).…”