Effects of alpha-galactosylceramide (KRN7000), interleukin-12 and interleukin-7 on phenotype and cytokine profile of human Valpha24+ Vbeta11+ T cells

The alpha-galactosylceramide KRN7000 was reported to be presented by CD1d to natural killer (NK) T cells, cells that are thought to play an important role in the rejection of malignant tumours and in the regulation of several autoimmune diseases. Here we analysed human peripheral blood (PB) NK T cells (Valpha24+ Vbeta11+ T cells) before and after a short-term culture in the presence of KRN7000. KRN7000 strongly activated PB Valpha24+ Vbeta11+ T cells and, when stimulated, the vast majority of these cells expressed interferon-gamma (IFN-gamma). Exposure of these KRN7000-cultured Valpha24+ Vbeta11+ T cells to interleukin-12 (IL-12), but not to IL-7, resulted in a relative increase in IFN-gamma-expressing Valpha24+ Vbeta11+ T cells, compared with IL-4-expressing Valpha24+ Vbeta11+ T cells, indicating a shift towards a T-helper type 1 (Th1) phenotype. KRN7000 strongly up-regulated the expression of the cytotoxic molecule granzyme B (GrB) in Valpha24+ Vbeta11+ T cells. Although IL-7 resulted in a decrease in GrB levels in KRN7000-cultured Valpha24+ Vbeta11+ T cells, IL-12 increased GrB levels in both Valpha24+ Vbeta11+ T cells and in Valpha24+ Vbeta11+ T-cell clones and increased cytotoxicity against hCD1d-transfected HeLa cells. Our data provide further insight into the characteristics of human Valpha24+ Vbeta11+ T cells and indicate that KRN7000 is a potent activator of Valpha24+ Vbeta11+ T cells. Combined with the established anti-tumour effects of KRN7000 in mouse models, these results may support the use of KRN7000 as an anti-tumour agent in man.

Human T lymphocyte priming in vitro by haptenated autologous dendritic cells

Dendritic cells (DC), generated from adherent peripheral blood mononuclear cells (PBMC) by culturing with granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4, were used to study in vitro sensitization of naive, hapten-specific T cells and to analyse cross-reactivities to related compounds. DC were hapten-derivatized with nickel sulphate (Ni) or 2-hydroxyethyl-methacrylate (HEMA), followed by tumour necrosis factor-alpha (TNF-alpha)-induced maturation, before autologous T cells and a cytokine cocktail of IL-1beta, IL-2 and IL-7 were added. After T cell priming for 7 days, wells were split and challenged for another 7 days with Ni or HEMA, and potentially cross-reactive haptens. Hapten-specificity of in vitro priming was demonstrated by proliferative responses to the haptens used for priming but not to the unrelated haptens. Highest priming efficiencies were obtained when both IL-4 and IL-12 were added to the cytokine supplement. Marked interferon-gamma (IFN-gamma) release (up to 4 ng/ml) was found when IL-12 was included in the cultures, whereas IL-5 release (up to 500 pg/ml) was observed after addition of IL-4 alone, or in combination with IL-12. Nickel-primed T cells showed frequent cross-reactivities with other metals closely positioned in the periodic table, i.e. palladium and copper, whereas HEMA-primed T cells showed distinct cross-reactivities with selected methacrylate congeners. Similar cross-reactivities are known to occur in allergic patients. Thus, in vitro T cell priming provides a promising tool for studying factors regulating cytokine synthesis, and cross-reactivity patterns of hapten-specific T cells.

Distribution of four polymorphisms in the tumour necrosis factor (TNF) genes in patients with inflammatory bowel disease (IBD)

In 153 patients with IBD, 64 with Crohn's disease (CD), and 89 with ulcerative colitis (UC), as well as in 54 healthy controls (HC), the frequencies of four known di-allelic polymorphisms in the genes for TNF-alpha and lymphotoxin alpha (LTalpha) were investigated. In the Dutch population, the alleles of these four polymorphisms are present in only five combinations, called TNF haplotypes: TNF-C, -E, -H, -I, -P. Furthermore, the relation with the presence of perinuclear anti-neutrophil cytoplasmic autoantibodies (P-ANCA) was studied. A small, but statistically significant, association between the polymorphism at position -308 in the promoter region of the TNF-alpha gene and UC was found. The frequency of the uncommon TNF-alpha -308 allele 2 was found to be decreased in patients with UC compared with HC (allele frequency of allele 2 in UC patients 0-15 versus 0.25 in HC, P=0.044). No significant differences in distribution of the TNF haplotypes were found between IBD patients and HC, although there was a tendency towards a higher frequency of the TNF-C haplotype in UC patients compared with controls (haplotype frequency 22% versus 13%; P=0.19). No statistically significant differences in distribution of the TNF haplotypes were observed between P-ANCA-positive and P-ANCA-negative UC patients. The strength of the associations indicates that TNF genes are not markers for the predisposition to suffer from IBD. They may, however, be markers of subsets of patients with UC and CD.

Suppression of lymphocyte proliferation by a retroviral p15E-derived hexapeptide

CKS-17 (LQNRRGLDLLFLKEGGL), a synthetic peptide derived from a conserved region of retroviral transmembrane proteins, has previously been shown to suppress several different immune effector mechanisms. The present study was undertaken to further delineate immunosuppressive site(s) of CKS-17. Overlapping hexapeptides covering the complete sequence of CKS-17 were synthesized. One CKS-17-derived hexapeptide, LDLLFL, suppressed ligand [CD3, interleukin (IL)-2]-induced lymphocyte proliferation. Spontaneous proliferation of transformed lymphoid cell lines, as well as cell lines from myeloid or epitheloid origin, was not inhibited by LDLLFL. Full suppression required the continuous presence of LDLLFL during culturing, and did not involve interference with monocyte function. Radiolabeling studies showed that the hexapeptide did not compete with IL-2 for IL-2 receptor binding. Most likely the LDLLFL motif interferes with steps shared by the IL-2 and CD3 receptor-induced signaling pathways. Since LDLLFL displays multiple immunosuppressive activities, it may constitute a biologically relevant immunosuppressive site of retroviral transmembrane proteins.

Reduced frequency of nickel allergy upon oral nickel contact at an early age

From animal studies we know that oral administration of T-dependent antigens before sensitization effectively induces systemic immune unresponsiveness. Such 'oral tolerance' is persistent, dose-dependent, antigen-specific and presumably T suppressor cell-mediated. Oral tolerance induction could be an effective way to prevent undesired T cell-mediated immune functions, such as playing a role in allograft reaction, autoimmune and allergic diseases. In the present study allergic contact hypersensitivity (ACH) to nickel, currently presenting the most frequent contact allergy in man, was chosen to establish the feasibility of oral prevention of undesired T cell-mediated immunity in man. Potentially tolerizing (oral nickel contacts via orthodontic braces) as well as sensitizing (ear piercing) events were studied retrospectively in 2176 patients attending nine European patch test clinics. Patients were interviewed by means of a confidential questionnaire. The results show that ear piercing strongly favoured development of nickel ACH. More importantly, patients having had oral contacts with nickel-releasing appliances (dental braces) at an early age, but only if prior to ear piercing, showed a reduced frequency of nickel hypersensitivity. Frequencies of other hypersensitivities, in particular to fragrance, were not affected. These results support our view that induction of specific systemic immunologic tolerance by timely oral administration of antigens is feasible in man.

Oral induction of immunological tolerance to chromium in the guinea pig

Metal alloys used in dentistry may elicit adverse side-effects. Contact allergic reactions to metals released from such alloys are among the most frequently encountered problems. In an earlier study, we observed that oral contacts with nickel or chromium salts did not sensitize, but rather decreased the risk of subsequent sensitization to these metals. In the present study, we focused on chromium allergy and extended our earlier observations by further dose-response studies. In addition, we compared different chromium valencies as to their potential oral tolerogenic effects. Development of immunological tolerance in chromium-fed guinea pigs was demonstrated by their inability to develop chromium hypersensitivity after a subsequent immunization attempt. For these studies, the techniques of immunization and skin testing were first improved. One feeding with a high dose of K2Cr2O7 (containing hexavalent chromium) was effective in full tolerance induction. In contrast, trivalent chromium (CrCl3) induced a distinctly lower degree of tolerance, whereas metallic chromium powder was not detectably tolerogenic after a limited number of feedings. Dose-frequency-response studies with K2Cr2O7 showed that full tolerance could also be induced by an increase in the number of feedings with sub-optimal tolerogenic doses. The present results therefore support our hypothesis that long-lasting oral contact with chromium-releasing metal alloys may ultimately result in strong immune tolerance to this metal in subjects without previous skin contact with it. This view is further supported by recent insights into the unique tolerogenicity of oral, as compared with gastro-intestinal, allergenic contacts.