Adherence of human monocytes and NK cells to human TNF-alpha-stimulated porcine endothelial cells.

Discordant xenograft models undergoing delayed rejection response are characterized by xenograft infiltration with host monocytes and NK cells, associated with the release of large quantities of pro-inflammatory cytokines, such as TNF-alpha. In the present study, human monocytes (PBMo)/NK cells (PBNK) isolated from peripheral blood and cultured porcine aortic endothelial cells (PAEC) treated with recombinant human TNF-alpha (rhTNF-alpha) were used to investigate their adhesive interactions and mAbs against porcine E-selectin, human CD11a and CD49d were used to test their relative contributions to such intercellular adhesions. The PBMo exhibited significantly greater adherence to resting (unstimulated) PAEC than PBNK. The rhTNF-alpha upregulated E-selectin and vascular cell adhesion molecule-1 (VCAM-1) expression on PAEC and augmented the adhesiveness of PAEC for PBMo and PBNK in a time- and dose-dependent manner. In mAb blocking assays, anti-E-selectin, anti-CD11a and anti-CD49d mAbs did not inhibit PBMo adherence to rhTNF-alpha-stimulated PAEC when used singly, but resulted in a maximal inhibitory effect when used in combination. Regarding PBNK, anti-E-selectin mAb had no marked influence on PBNK adherence. The combined use of anti-CD11a and anti-CD49d mAbs produced additive reduction in the PBNK binding to rhTNF-alpha-stimulated PAEC, even to far below baseline (unstimulated) levels. Therefore, it is concluded that human TNF-alpha promotes the adhesiveness of PAEC for human monocytes and NK cells and that the mechanism underlying the increased adherence differs for PBMo and PBNK.