Porcine Embryonic Brain Cell Cytotoxicity Mediated by Human Natural Killer Cells

Abstract

Intracerebral transplantation of porcine embryonic dopamine-producing neurons has been suggested as a method to treat patients with Parkinson's disease. Even though the brain is an immunologically privileged site, neuronal xenografts are usually rejected within a few weeks. T cells are important for this process, but the exact cellular events leading to rejection are poorly characterized. Brain cells from ventral mesencephalon of 26-27-day-old pig embryos were used as target cells in flow cytometry-assessed cytotoxicity assays using non- and IL-2-activated CD3- CD16+ CD56+ human natural killer (NK) cells as effector cells. The ability of human NK cells to kill pig embryonic brain cells by antibody-dependent cellular cytotoxicity (ADCC) in the presence of nondepleted and anti-Gal alpha1,3Gal antibody-depleted human blood group AB serum (AB serum) was evaluated using the same assay. Both nondepleted and anti-Gal alpha1,3Gal antibody-depleted AB serum could mediate ADCC of pig embryonic VM cells when human NK cells were used as effector cells. Nonactivated NK cells did not show any direct cytotoxic effect on freshly isolated VM cells, whereas IL-2-activated NK cells killed approximately 50% of the VM cells at an effector-to-target ratio of 50:1 in a 4-h cytotoxicity assay. Activation of VM cells by TNF-alpha did not change their sensitivity to human NK cell cytotoxicity. Human NK cells may thus contribute to a cellular rejection of pig neuronal xenografts by ADCC, or following IL-2 activation, by a direct cytotoxic effect.

Enhanced Survival of Porcine Neural Xenografts in Mice Lacking CD1d1, But No Effect of NK1.1 Depletion

“…Porcine microglia and endotheial cells express high amounts of DISCUSSION the α-Gal epitope (44), and recent evidence also suggests that α-Gal is present in small amounts on porcine Our results show that NK1.1+ cells are not important neurons (R. Barker, personal communication). It has mediators of the rejection process of porcine neural xebeen shown that humans have preformed antibodies nografts in mice.…”

“…This is in contrast to the situation for against at least two additional epitopes present on neural primarily vascularized organ xenografts, where NK cells tissue, and that NK cell-mediated antibody-dependent are crucial mediators of acute vascular rejection (33). In killing in vitro can take place in the absence of α-Gal this aspect, rejection of discordant secondarily vascularantibodies (44). Hence, the pig-to-mouse and the pig-toized cellular neural xenografts seems less complicated human in vivo xenograft combinations are not likely to than rejection of many other types of xenografts.…”

“…lar to the ones in this study. Thus, although it has been Glial cells, astrocytes as well as microglia cells, may shown in vitro that human NK cells can kill porcine secrete neurotrophic factors such as glial-derived neuroneural tissue (44), it seems that NK cell-mediated mechtrophic factor (4), which has been shown to improve the anisms are less important in vivo. In acute vascular resurvival of allogeneic transplants (39).…”

“…these cells was not addressed. In an in vitro study by C57BL/6 (Möllegaard, DK) (n = 16), C57BL/6 treated Sumitran et al (44), it was shown that human NK cells with an anti-NK1.1 antibody (n = 16), CD1.1−/− mutant were cytotoxic to porcine neurons both via antibody mice (C57BL/6 × 129/Sv, generously provided by Luc binding and directly, when activated by IL-2. Tumors van Kaer) (n = 14), and wild-type littermates (n = 14).…”

Activated Porcine Embryonic Brain Endothelial Cells Induce a Proliferative Human T-Lymphocyte Response

“…The (PBMEC) might be highly immunogenic in the pig-tohuman situation, where the relationship between direct involvement of immunoglobulins (31,54), complement (1) (Larsson, Sumitran-Holgersson, Korsgren, Holgersand indirect antigen recognition is more balanced. In the present study, our aim was to determine whether son, and Widner, manuscript in preparation), natural killer (NK) cells (53), and NK T cells (29) in neural xeno-PBMEC could induce a human T-cell response via the direct pathway of antigen recognition. Resting PBMEC, graft rejection have also been suggested, as reviewed in Brevig et al (4).…”