Characterization of human killer cell reactivity against porcine target cells: differential modulation by cytokines

Abstract

The cytotoxic cell response to porcine cells by human lymphocytes, and the modulation of cytolytic cellular activity by human cytokines were investigated. Human peripheral blood mononuclear cells (PBMC) and purified lymphocyte subsets were co-cultured with fresh irradiated porcine stimulator cells and examined for the development of lytic activity and for their proliferative response. Porcine target cells included a new cell line, MS-PBMC-J2 (designated J2; SLA-DR+MHC class I+CD2+CD3 CD8+CDI6+CD45+), aortic and microvascular endothelial cells. Initial results showed that natural killer (NK) cells were fivefold more efficient in killing porcine target cells compared with T cells. IL-12 augmented the killing of porcine target cells by human NK cells beyond that induced by stimulation with cells alone. In contrast, IL-2 and IL-15 often induced substantial human NK cell mediated killing of porcine target cells, including endothelial cells in the case of IL-2 where such targets were examined, even in the absence of stimulator cells. Finally, neither IL-18 nor IL-8 had any effect beyond background on NK cell mediated killing of porcine target cells. These findings show that cytokines that would be produced in a xenograft setting clearly modulate the ability of human cytolytic cells to kill porcine targets. In addition, fresh unstimulated human NK cells lysed J2 and porcine aortic endothelial cells, but not porcine microvascular endothelial cells, suggesting the possibility of rapid attack of xenografts by NK cells, and differential susceptibility of endothelial cells from different vascular structures to this attack.

Human NK cells can lyse porcine endothelial cells independent of their expression of Galα(1,3)‐Gal and killing is enhanced by activation of either effector or target cells

“…The natural killer (NK) cells mediate human anti-porcine activity in vitro [4][5][6][7], and mediate xenograft rejection in model systems in vivo directly [8][9][10][11], or through antibody-dependent mechanisms [12][13][14]. Whether recognition of aGal is involved in the lysis of porcine target cells by human NK cells has been controversial.…”

The cellular rejection of xenografts – recent insights

“…The expression of non‐classical human leukocyte antigen (HLA) G1 on porcine EC has been shown to partially reduce the lytic activity [2] and the adhesion [3] of human NK cells to porcine EC. In addition, the inflammatory environment observed during xenograft rejection is likely to further potentiate NK reactivity, since pro‐inflammatory cytokines [4] and the level of E‐selectin expression on porcine EC [5] clearly enhance lytic activity of human NK cells against porcine targets.…”

Effect of Redox Modulation on Xenogeneic Target Cells: The Combination of Nitric Oxide and Thiol Deprivation Protects Porcine Endothelial Cells from Lysis by IL-2-Activated Human NK Cells

“…NK cells were purified as described previously (14). Briefly, PBMC were obtained from buffy coats obtained from healthy human donors (Blood Bank, National Institutes of Health, Bethesda, MD) by centrifugation over Ficoll-Hypaque (Amersham Pharmacia Biotech, Piscataway, NJ).…”

“…NK cells have been implicated as mediators of rejection in concordant and discordant xenograft rodent models in vivo and in vitro (6 -9) and may participate in the human antiporcine rejection response (10 -12). NK cells appear important in the rejection of porcine hearts transplanted into baboons (13) and have been reported to lyse porcine target cells with or without activation, in the presence or absence of human serum containing natural Abs (1,10,11,14,15). These findings suggest that NK cells may contribute to the pathogenesis of xenograft rejection.…”

“…Pigs have been suggested as a primary potential source of xenografts for use in humans, but porcine ECs are susceptible to lysis by human NK cells in vitro (14,18,19), and, conversely, human NK cells activate porcine ECs (20,21). Therefore, it is important to gain a further understanding of the interaction between porcine ECs and human NK cells to begin to devise means by which delayed xenograft rejection may be inhibited or prevented.…”