Bilberry extract, its major polyphenolic compounds, and the soy isoflavone genistein antagonize the cytostatic drug erlotinib in human epithelial cells

Erlotinib (Tarceva®) is a chemotherapeutic drug approved for the treatment of pancreatic cancer and non-small cell lung cancer. Its primary mode of action is the inhibition of the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase (RTK). Recently, RTK-inhibiting polyphenols have been reported to interact synergistically with erlotinib. Furthermore some anthocyanidins and anthocyanin-rich berry extracts have been reported to inhibit tyrosine kinases, including the EGFR, which raises the question of potential interactions with erlotinib. Polyphenol-rich preparations such as berry- or soy-based products are commercially available as food supplements. In the present study we tested a bilberry extract, its major anthocyanin and potential intestinal degradation products, as well as genistein, with respect to possible interactions with erlotinib. Cell growth inhibition was assessed using the sulforhodamine B assay, while interactions with EGFR phosphorylation were analyzed by SDS-PAGE/western blotting with subsequent immunodetection. Genistein, bilberry extract, delphinidin-3-O-glucoside and delphinidin were found to antagonize erlotinib whereas phloroglucinol aldehyde was found to enhance cytostatic effects of the drug on human epithelial A431 cells. Genistein also antagonized the EGFR inhibitory effects of erlotinib, whereas bilberry anthocyanins showed no significant interactions in this regard. Our data indicate that different polyphenols are potentially able to impair the cytostatic effect of erlotinib in vitro. Genistein interacts via the modulation of erlotinib-mediated EGFR inhibition whereas bilberry anthocyanins modulated the growth-inhibitory effect of erlotinib without affecting EGFR phosphorylation, thus indicating a different mechanism of interference.

Detailed analysis of the effects of Glu/Lys beta69 human leukocyte antigen-DP polymorphism on peptide-binding specificity

The polymorphism at position beta69 of the human leukocyte antigen (HLA)-DP molecule has been associated with susceptibility to several immune disorders and alloreactivity. Using molecular modeling, we have predicted a detailed structure of the HLA-DP2 molecule (carrying Glubeta69) complexed with class II associated invariant chain derived peptide (CLIP) and compared it with the form carrying Lys at beta69 (HLA-DP2K69). Major changes between the two models were observed in the shape and charge distribution of pocket 4 and of the nearby pocket 6. Consequently, we analyzed in detail the peptide-binding specificities of both HLA-DP molecules expressed as recombinant proteins. We first determined that the minimum peptide-binding core of CLIP for both HLA-DP2 and DP2K69 is represented by nine aminoacids corresponding to the sequence 91-99 of invariant chain (Ii). We then assessed the peptide-binding specificities of the two pockets and determined the role of position beta69, using competition tests with the Ii-derived peptide CLIP and its mutated forms carrying all the aminoacidic substitutions in P4 and P6. Pocket 4 of HLA-DP2 showed high affinity for positively charged, aromatic, and polar residues, whereas aliphatic residues were disfavored. Pocket 4 of the DP2K69 variant showed a reduced aminoacid selectivity with aromatic residues most preferred. Pocket 6 of HLA-DP2 showed high affinity for aromatic residues, which was increased in DP2K69 and extended to arginine. Finally, we used the experimental data to determine the best molecular-modeling approach for assessing aminoacid selectivity of the two pockets. The results with best predictive value were obtained when single aminoacids were evaluated inside each single pocket, thus, reducing the influence of the overall peptide/ major histocompatibility complex interaction. In conclusion, the HLA-DPbeta69 polymorphism plays a fundamental role in the peptide-binding selectivity of HLA-DP. Furthermore, as this polymorphism is the main change in the pocket 4 area of HLA-DP, it could represent a supertype among HLA-DP molecules significantly contributing to the selection of epitopes presented in the context of this HLA isotype.

Role of donor and recipient antigen-presenting cells in priming and maintaining T cells with indirect allospecificity

BACKGROUND

It has been suggested that the sensitization of recipient T lymphocytes against peptides derived from allogeneic major histocompatibility complex (MHC) antigens in the context of self-MHC molecules may contribute to the pathogenesis of chronic allograft rejection. The purpose of this study was to quantitate and characterize the indirect alloresponse in renal transplantation.

METHODS

An HLA-A2-negative patient whose A2-positive kidney transplant failed as a result of chronic rejection was selected for this study. T-cell clones were raised using a cocktail of peptides corresponding to polymorphic regions of the A2 sequence and studied by measuring their proliferation using [3H]thymidine incorporation. The presence in vivo of HLA-A2-specific T cells was assessed using limiting dilution analysis.

RESULTS

T-cell clones were specific for a single peptide of HLA-A2, residues 92-120, and restricted by HLA-DRB1*1502. The frequency of interleukin-2-secreting T cells specific for this A2 peptide was 1:86,000, only 2-fold lower than that measured against the recall antigen tetanus toxoid. Capitalizing on the similarity of the donor and recipient DR15 alleles (DRB1*1501 and 1502), the question was addressed as to how these T cells had been primed in vivo. Although the large majority of clones responded to A2 synthetic peptide presented by both DR15 alleles, only 3 of 10 clones responded to cells co-expressing DRB1*1501 and A2.

CONCLUSION

These data suggest that antigen presentation by recipient APCs is responsible for maintaining T cells with indirect allospecificity in vivo and that, in the context of partial DR matching, indirect presentation by the parenchymal cells of the graft may serve to induce tolerance in T cells with indirect allospecificity.

Expression of recombinant anti-E-selectin single-chain Fv antibody fragments in stably transfected insect cell lines

We have investigated the possibility of improving the yield of properly folded recombinant single chain Fv fragments (sFv) of an antibody by expressing the protein in stably transfected Drosophila melanogaster SC-2 cells. The DNA encoding the variable regions of the 1.2B6 anti-E-selectin antibody were used to generate a recombinant sFv. This construct was cloned into the pHEN1 vector for expression in Escherichia coli and the pRmHa-3 vector to generate stably transfected Drosophila SC-2 cell lines. Following expression in the bacterial system, and using standard refolding protocols to obtain active material, it was shown that the majority of the sFv formed non-covalent aggregates. In addition SDS-PAGE analysis indicated that even the monomeric material was heterogeneous. In contrast, expression of sFv in Drosophila SC-2 cell lines allowed purification of active sFv directly from the culture supernatant. Only a small proportion of the sFv formed aggregates, and the purified material was homogeneous as determined by SDS-PAGE. Thus the use of stably transfected insect cells has a number of potential advantages in expressing recombinant antibody fragments.

Major histocompatibility complex class II-dependent unfolding, transport, and degradation of endogenous proteins

We have analyzed the ability of major histocompatibility (MHC) class II molecules to capture proteins in the biosynthetic pathway and whether this may be associated with MHC class II-dependent antigen processing. When coexpressed with HLA-DR 4 molecules in HeLa cells, influenza hemagglutinin was inhibited from folding and trimerization in the biosynthetic pathway, targeted to endosomal compartments, and rapidly degraded. Due to the interaction with MHC class II molecules, therefore, unfolded forms of hemagglutinin were bypassing the quality control mechanism of the secretory pathway. More important, however, the transport, endocytosis, and rapid degradation of unfolded hemagglutinin in the presence of MHC class II molecules suggest that proteins captured in the endoplasmic reticulum by class II molecules may become substrates for antigen processing and presentation to CD4-positive T cells. In insect cells we show that this phenomenon is not restricted to a few proteins such as hemagglutinin. A highly heterogeneous mixture of proteins from the endoplasmic reticulum including coexpressed hemagglutinin can form stable complexes with soluble HLA-DR alpha and beta chains that were transported into the supernatant. This mechanism may gain biological significance in abnormal situations associated with accumulation of unfolded or malfolded proteins in the endoplasmic reticulum, for example during viral infections.

In the absence of the invariant chain, HLA-DR molecules display a distinct array of peptides which is influenced by the presence or absence of HLA-DM

The independent influences of invariant chain (Ii) and HLA-DM molecules on the array of naturally processed peptides displayed by HLA-DR molecules were studied using transfected cell lines. The absence of Ii led to an altered set of HLA-DR-bound peptides as judged by the discriminating responses of alloreactive T cell clones. While most T cell clones raised against DR+Ii+DM+ peripheral blood mononuclear cells (PBMC) failed to respond to DR+Ii-DM- cells, T cell clones raised against DR+Ii-DM- transfectants were not stimulated by DR+Ii+DM+ cells. Furthermore, coexpression of HLA-DM with HLA-DR1 in the absence of Ii augmented responses of anti-PBMC T cell clones but inhibited allorecognition by T cell clones raised against DR+Ii-DM- transfectants. The conformational integrity of the class II molecules, as judged by serology, suggests that the patterns of reactivity of the T cell clones reflect specificity for different alloantigen-bound peptides. Hence, discordant regulation of expression of major histocompatibility complex class II, Ii, and HLA-DM molecules in vivo may lead to the display of novel self-peptides and possible interruption of self-tolerance.

CD4 monoclonal antibody VIT4 in human alloimmune response in vitro and in vivo

In the present report the immunosuppressive effects of the murine anti-human CD4 monoclonal antibody (mAb) VIT4 on human alloimmune response in vitro were analyzed. Moreover, the antibody was tested for its activity to prolong allograft survival in seven patients with steroid-refractory allograft rejection. VIT4 inhibited the proliferative response to alloantigens in the mixed lymphocyte reaction (MLR) in a dose-dependent manner. At concentrations of 1 and 10 micrograms/ml VIT4 blocked MLR by 55 +/- 11% and 77 +/- 1%, respectively. Also alloantigen-specific proliferation of in vitro- generated memory T cells was dose-dependently reduced to 23 +/- 1% at a VIT4 concentration of 100 micrograms/ml. Furthermore, at the same dose level VIT4 blocked proliferation of antigen-specific short-term alloreactive CD4+ cell lines and significantly inhibited the in vitro generation of cytotoxic T lymphocytes (CTL). In a pilot study VIT4 (5 mg/d i.v.) was administered to 7 patients with steroid-refractory allograft rejection for 14 days. In 4 of 7 patients graft function transiently improved and graft survival in all patients was prolonged to a mean of 694 days (range 128-2163) from the beginning of the VIT4 treatment. In the light of our in vitro results and the preliminary clinical data, further clinical trials using higher antibody doses are greatly warranted to assess the efficacy of anti-CD4 mAb VIT4 in the treatment of allograft rejection.

Endogenous pathway of class II presentation

Assembly, targeting and peptide loading of MHC class II molecules is controlled by a series of mechanisms and molecular interactions that inhibit the binding of peptides or proteins in the ER or secretory compartment. As a consequence, the major site of peptide binding to class II molecules is in the endosomal/lysosomal compartment. The barrier, however, between exogenous and endogenous antigen presentation by MHC class II molecules does not seem to be as tight as for MHC class I, and several different mechanisms may contribute to MHC class II presentation of endogenous antigens. Although limited, the possibility of presentation of endogenous antigens may nevertheless be important in viral infections and in tumours, for the recruitment of CD4-positive helper T-cells. This may also apply when unfolded or misfolded proteins accumulate in the ER and compete with the invariant chain for binding to MHC class II molecules. The potential relevance of this pathway to triggering autoimmune reactions has yet to be explored.

Intradermal gene immunization: the possible role of DNA uptake in the induction of cellular immunity to viruses

The skin and mucous membranes are the anatomical sites were most viruses are first encountered by the immune system. Previous experiments have suggested that striated muscle cells are unique among mammalian cell types in their capacity to take up and express free DNA in the absence of a viral vector or physical carrier. However, we have found that mice injected into the superficial skin with free (naked) plasmid DNA encoding the influenza nucleoprotein gene had discrete foci of epidermal and dermal cells, including cells with dendritic morphology, that contained immunoreactive nucleoprotein antigen. A single intradermal administration of 0.3-15 micrograms of free plasmid DNA induced anti-nucleoprotein-specific antibody and cytotoxic T lymphocytes that persisted for at least 68-70 weeks after vaccination. Intradermal gene administration induced higher antibody titers than did direct gene injection into skeletal muscle and did not cause local inflammation or necrosis. Compared with control animals, the gene-injected mice were resistant to challenge with a heterologous strain of influenza virus. These results indicate that the cells of the skin can take up and express free foreign DNA and induce cellular and humoral immune responses against the encoded protein. We suggest that DNA uptake by the skin-associated lymphoid tissues may play a role in the induction of cytotoxic T cells against viruses and other intracellular pathogens.

Structural analysis of anti-DR1 allorecognition by using DR1/H-2Ek hybrid molecules. Influence of the beta 2-domain correlates with CD4 dependence

A segmental analysis of the key regions of HLA-DR1 that control T cell allorecognition was performed by using a series of transfected cell lines expressing the products of recombinant DRB/H-2Eb genes, paired with either DR alpha or H-2E alpha. Four of eight human T cell clones tolerated substitution of the H-2E alpha chain, but only one clone showed any response to the DR alpha/H-2E beta k dimer. Both the membrane-proximal and the membrane-distal domains of the beta-chain played an important part in stimulating these clones. The response of four of eight clones was markedly inhibited by substitution of the H-2E beta 2 for the DR beta 2 domain. This inhibition showed a complete correlation with the sensitivity of the clones to inhibition by anti-CD4 mAb. Taken together, these results suggest that the interaction site for CD4 may include residues on the beta 2-domain. Introduction of H-2Ek sequence into either half of the beta 1-domain led to a complete loss of response by all but two of the clones. This is consistent with these clones having dual specificity for exposed DR1-specific polymorphisms and for DR1-bound peptides. The pattern of response of one of the clones suggested that indirect conformational effects on the alpha 1-domain may also contribute to the influence of the amino-terminal half of the beta 1-domain on T cell recognition. In the presence of H-2E alpha, this clone responded more strongly when the amino-terminal half of the beta 1-domain was of H-2Ek rather than DR1 sequence. This implies that species matching of the floor of the beta 1-domain with the alpha-chain is more important than the presence of the alpha-chain of the parental species.

Structural analysis of anti-DR1 allorecognition by using DR1/H-2Ek hybrid molecules. Influence of the beta 2-domain correlates with CD4 dependence

A segmental analysis of the key regions of HLA-DR1 that control T cell allorecognition was performed by using a series of transfected cell lines expressing the products of recombinant DRB/H-2Eb genes, paired with either DR alpha or H-2E alpha. Four of eight human T cell clones tolerated substitution of the H-2E alpha chain, but only one clone showed any response to the DR alpha/H-2E beta k dimer. Both the membrane-proximal and the membrane-distal domains of the beta-chain played an important part in stimulating these clones. The response of four of eight clones was markedly inhibited by substitution of the H-2E beta 2 for the DR beta 2 domain. This inhibition showed a complete correlation with the sensitivity of the clones to inhibition by anti-CD4 mAb. Taken together, these results suggest that the interaction site for CD4 may include residues on the beta 2-domain. Introduction of H-2Ek sequence into either half of the beta 1-domain led to a complete loss of response by all but two of the clones. This is consistent with these clones having dual specificity for exposed DR1-specific polymorphisms and for DR1-bound peptides. The pattern of response of one of the clones suggested that indirect conformational effects on the alpha 1-domain may also contribute to the influence of the amino-terminal half of the beta 1-domain on T cell recognition. In the presence of H-2E alpha, this clone responded more strongly when the amino-terminal half of the beta 1-domain was of H-2Ek rather than DR1 sequence. This implies that species matching of the floor of the beta 1-domain with the alpha-chain is more important than the presence of the alpha-chain of the parental species.

Limited regions of the alpha 2-domain alpha-helix control anti-A2 allorecognition: an analysis using a panel of A2 mutants

The regions of the HLA-A2 molecule controlling anti-A2 alloreactivity were explored using naturally occurring allelic variants of HLA-A, and a panel of transfectants expressing the products of A2.1 genes that had been mutated at multiple positions encoding residues in the alpha 2 domain alpha-helix. As a means of detecting distant conformational effects, these altered A2.1 molecules were also examined serologically. Amino acid substitutions at the carboxy-terminal end of the alpha 2 domain alpha-helix led to diminished staining with the monoclonal antibody (mAb) MA2.1. The epitope for this antibody has previously been mapped to the alpha 1 domain alpha-helix (residues 62-65). This suggests that interdomain contacts may cause conformational alteration, and that mutants can have distant, as well as local effects. Of the 24 positions where substitutions were made, only six led to loss of the anti-A2 alloresponse by the three clones and three lines that were tested. In addition, the mutations that altered the MA2.1 epitope, located on the alpha 1 domain alpha-helix, did not inhibit allorecognition. This suggests that a limited number of regions on the A2.1 molecule are responsible for allodeterminant expression. The most influential substitutions were those at positions 152, 154, 162, and 166. It is notable that three of these are predicted to be T-cell receptor (Tcr)-contacting residues, and one (152) to contribute to peptide binding. These results suggest that the specificity of alloreactive T cells is determined by exposed polymorphisms, directly contacted by the Tcr, and by concealed polymorphisms which influence peptide binding.

Further evidence for lymphokine overproduction in severe aplastic anemia

Interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF) are lymphokines with a potent hematopoietic progenitor cell suppressive capacity. In untreated and immunosuppressed patients with severe aplastic anemia (SAA) and in control individuals we measured (a) serum levels of IFN-gamma and TNF and its production by peripheral blood mononuclear cells (PBMNC); (b) serum levels of neopterin, a product that reflects endogenous IFN production; (c) resting and activated lymphocyte subpopulations; and (d) serum levels of soluble interleukin-2 receptor (IL-2R). Serum levels of IFN and TNF did not differ significantly in untreated and treated SAA patients and control individuals. Spontaneous and phytohemagglutinin-induced production of IFN and TNF by PBMNC, however, were highly increased in both untreated and treated SAA patients. Increased and decreased neopterin serum levels in untreated and treated SAA patients, respectively, suggest modulation of endogenous lymphokine release subsequent to immunosuppression. HLA-DR+ antigen was mainly expressed by CD8 T cells. Circulating numbers of activated (CD4 and CD8) T cells and serum levels of IL-2R were not increased in both untreated and treated SAA patients. The proportion of HLA-DR+ T cells in the PBMNC of untreated SAA patients correlated with the extent of lectin-induced IFN production. Although we were unable to confirm previous reports in SAA on (a) detectable IFN in blood and bone marrow serum, (b) improvement of stem cell growth upon neutralization of endogenous IFN, (c) absolutely increased numbers of circulating activated T cells, and (d) normalization of these abnormalities subsequent to successful immunosuppression, our data clearly support previous reports on abnormal lymphokine production in severe aplastic anemia. Our failure to relate this phenomenon to the severity of disease states, however, further raises doubts on the pathogenetic significance of lymphokine overproduction in SAA.

In situ immune complexes, lymphocyte subpopulations, and HLA-DR-positive epithelial cells in Hashimoto thyroiditis

Surgical specimens from thyroid glands from seven patients with Hashimoto thyroiditis and two patients with non-autoimmune colloid goiter were analyzed by immunohistologic techniques (direct and indirect immunofluorescence and immunoperoxidase tests) using polyclonal antisera against total immunoglobulin, Ig classes (IgM, IgD, IgG, and IgA), and complement component C3 and monoclonal antibodies specific for B cells, T cell subpopulation, macrophages, natural killer cells, granulocytes, and HLA-DR antigen. Complement-fixing immune complexes (IgG+, C3+) were noted predominantly in areas with only slight destruction and only moderate lymphoid infiltration of thyroid follicles. In areas with intense lymphoid infiltration of thyroid follicles, where many well-developed germinal centers and significant perivascular lymphoid infiltration were seen, immune complexes were scarce. In these latter areas T helper cells (OKT4+, Leu3a+), were more abundant than T cytotoxic/suppressor cells (OKT8+), macrophages (OKM1+), and plasma cells (IgG+); only a few B lymphocytes (smIgM+, smIgD+), granulocytes (ViMD5+), and natural killer cells (VEP13+, Leu7+) were noted in the interstitium between thyroid follicles, intruding between thyroid follicular epithelial cells and merging into the thyroid follicular lumen. Many activated T cells (OKT10+, HLA-DR+) were present in these areas of advanced destruction. HLA-DR antigen expression was seen on macrophages, tissue reticulum cells, vascular endothelial cells, lymphoid cells, and, most interestingly, on thyroid epithelial cells. Normal thyroid epithelial cells did not express HLA-DR. Only a few epithelial cells in the vicinity of lymphoid infiltrations were HLA-DR+ in early stages of Hashimoto thyroiditis, and the number of HLA-DR+ epithelial cells was significantly increased in advanced stages of the disease. In our present report the potential role of HLA-DR+ thyroid epithelial cells for the in situ stimulation of the immune system within the thyroid gland of patients with Hashimoto thyroiditis is discussed, and it is hypothesized that HLA-DR+ thyroid epithelial cells may be an important factor for the progression and self-perpetuation of the disease, which is probably initiated by humoral components of the immune system but further propagated by cellular immunopathologic mechanisms.

Nonthyroid autoantibodies in obese strain (OS) chickens

Organ-specific autoantibodies (AAb) to thyroid and non-thyroid antigens of various endocrine and exocrine glands (glandular stomach, pancreas, adrenal, parathyroid, and striated muscle) were determined by different serological procedures in sera from Obese strain (OS), Cornell C strain (CS), normal inbred strains (CC and CB), and outbred normal White Leghorn (NWL) chickens. Thyroglobulin autoantibodies (Tg-AAbs), evaluated by immunodiffusion, passive hemagglutination, enzyme-linked immunosorbent assay, and indirect immunofluorescence, as well as other organ-specific AAbs determined by indirect immunofluorescence, predominated in OS chickens. Tg-AAbs were found in the highest frequency, thyroid microsomal AAbs in intermediate frequency, and the other organ-specific AAbs in low frequency in OS chickens. Thyroid and non-thyroid organ-specific AAbs were found only occasionally in control chickens and then only in low titers. Thus, spontaneous autoimmune thyroiditis of OS chickens correlates closely with human Hashimoto thyroiditis not only in respect to AAbs to thyroid antigens but also to nonthyroid organ-specific antigens. Non-organ-specific AAbs, such as antinuclear antibodies, antibodies to chicken red blood cell nuclei, mitochondrial AAbs, smooth muscle antibodies, and reticulin AAbs occur in high frequency in all strains of chickens tested. Even a slight prevalence in NWL chickens was seen, indicating that the abnormal immune response in OS chickens is restricted to organ-specific antigens of the thyroid gland and in some cases also to other exocrine or endocrine glands.

Studies on the cytochrome P-450 product complexes formed during the metabolism of N,N-dimethylaniline

The oxidative metabolism of N,N-dimethylaniline by partially solubilized cytochrome P-450 from rabbit liver was found to be associated with the formation of a 424- and 448-nm product adduct of the hemoprotein. From the effects of temperature, hydrogen ion concentration, n-octylamine, extraction of the enzyme preparations with organic solvents and pretreatment of the animals with inducers of drug metabolism on both the formation of the spectral species and the enzymic C- and N-oxidation of N,N-dimethylaniline it is concluded that the 424-nm spectral change is generated from an intermediate in the C-oxidation reaction, whereas formation of the 448-nm spectral perturbation is the result of binding to cytochrome P-450 of a metabolite arising from N-oxidation of the arylamine; N-dealkylation of the parent amine is not a obligatory intermediary step in 448-nm complex formation. The 448-nm ferrohemochrome is supposed to be formed through coordination of the N-oxidized intermediate via the oxygen atom. This type of interaction appears to require considerably stronger thermal activation as compared with the 424-nm complex. The 448-nm product adduct of cytochrome P-450 is unstable in the ferric state or in the presence of sodium dithionite.