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Minor histocompatibility (H) antigens crucially affect the outcome of human leukocyte antigen (HLA)-identical allogeneic stem cell transplantation (SCT). To understand the basis of alloimmune responses against minor H antigens, identification of minor H peptides and their antigenicity-determining mechanisms is essential. Here we report the identification of HA-3 and its encoding gene. The HA-3 peptide, VTEPGTAQY (HA-3T), is encoded by the lymphoid blast crisis (Lbc) oncogene. We thus show for the first time that a leukemia-associated oncogene can give rise to immunogenic T-cell epitopes that may have participated in antihost and antileukemic alloimmune responses. Genotypic analysis of HA-3- individuals revealed the allelic counterpart VMEPGTAQY (HA-3M). Despite the lack of T-cell recognition of HA-3- cells, the Thr-->Met substitution had only a modest effect on peptide binding to HLA-A1 and a minimal impact on recognition by T cells when added exogenously to target cells. This substitution did not influence transporter associated with antigen processing (TAP) transport, but, in contrast to the HA-3T peptide, HA-3M is destroyed by proteasome-mediated digestion. Thus, the immunogenicity of minor H antigens can result from proteasome-mediated destruction of the negative allelic peptide.

The adhesive interactions between phagocytes and endothelial cells (EC) can be modulated by inflammatory cytokines and chemotactic proteins which are released during an inflammatory response. The aim of the present study was to investigate first whether the adhesive properties of granulocytes and monocytes from asthma patients for vascular endothelial cells differ from those of phagocytes from healthy individuals. Furthermore, we studied whether the chemokines interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) can affect the binding of phagocytes to EC. No differences were observed in binding of phagocytes from asymptomatic or symptomatic asthma patients and from healthy individuals to non-stimulated or cytokine-stimulated EC. Incubation of granulocytes with IL-8 did not influence their adhesion to non-stimulated EC but inhibited the adhesion of granulocytes to IL-1-stimulated EC. Incubation of monocytes with MCP-1 did not affect their adhesion to non-stimulated or cytokine-stimulated EC. Our results indicate that adhesion of phagocytes to EC depends on the activation state of the endothelial cells but not on the origin of the phagocytes, since there were no differences in the adhesion of phagocytes from asthma patients and healthy individuals to non-stimulated or cytokine-stimulated EC.

Upregulation of adhesion molecule expression on endothelial cells (EC) and circulating leukocytes, by locally produced inflammatory mediators, may result in the enhanced infiltration of leukocytes into tissue, e.g. the airways of asthma patients. The present study investigates whether the expression of adhesion molecules on granulocytes and monocytes from asthma patients is affected by chemotactic factors, i.e. interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1). Flow cytometric analysis showed that the intrinsic expression of the various adhesion molecules on peripheral blood phagocytes from asthma patients was not different from that of healthy individuals. However, stimulation of monocytes with MCP-1 resulted only in upregulation of the expression of CD14 on monocytes from symptomatic asthma patients but not on monocytes from asymptomatic asthma patients and healthy individuals. Stimulation of granulocytes with IL-8 did not change the expression of the various beta 1- and beta 2-integrin molecules, such as VLA-4, LFA-1, CR3 and p150,95. Since earlier studies have shown that CD14 on monocytes mediates monocyte adhesion to activated vascular EC the present findings suggest that during the active phase of asthma upregulation of CD14 on monocytes by MCP-1 may lead to an increased adhesion of monocytes to vascular endothelium and their subsequent transendothelial migration into the tissue of the airways.

The altered expression pattern of the Epithelial Cell Adhesion Molecule (Ep-CAM) and the Carcinoembryonic Antigen (CEA) on tumor cells of epithelial origin as compared to normal epithelia may permit T cells to preferentially recognize and lyse these tumor cells. The binding affinity for human leucocyte antigen A2.1 (HLA-A*0201) and the capacity to form stable peptide-major histocompatibility complex (MHC) interactions with this molecule were tested for 410 Ep-CAM-derived sequences, including an overlapping set of 9 amino-acid-long peptides, and 73 CEA-derived peptides fulfilling the HLA-A*0201 motif. Peptides with a high binding affinity and a low peptide-MHC dissociation rate were subsequently tested for their immunogenicity in HLA-A*0201Kb transgenic mice. One Ep-CAM-derived peptide and 1 CEA-derived peptide were able to reproducibly induce peptide-specific cytotoxic T cells (CTL) in these mice. This indicates that EpCAM and CEA are potential target antigens for CTL-mediated immunotherapy of epithelial cancers.