Identification of a novel HLA-B60-restricted T cell epitope of the minor histocompatibility antigen HA-1 locus

The polymorphic minor histocompatibility Ag HA-1 locus encodes two peptides, HA-1(H) and HA-1(R), with a single amino acid difference. Whereas the immunogenicity of the HA-1(R) allele has not yet been shown, the nonameric HA-1(H) peptide induces HLA-A2-restricted cytotoxic T cells in vivo and in vitro. It is not known whether the mHag HA-1(H) or HA-1(R) associates with other HLA class I molecules. Therefore, the polymorphic regions of both HA-1 alleles were analyzed to identify HLA class I binding peptides that are properly processed by proteasomal degradation. Peptide binding analyses were performed for all nonameric HA-1(H/R) peptides for binding to nine HLA class I molecules with >10% prevalence in the Caucasian population and for seven nonameric/decameric HA-1(H/R) peptides predicted to bind to HLA-A3, -B14, and -B60. Only the nonameric KECVL(H)/(R)DDL and decameric KECVL(H)/(R)DDLL peptides showed strong and stable binding to HLA-B60. In vitro digestion of 29-aa-long HA-1 peptides by purified 20S proteasomes revealed proper cleavage at the COOH termini of both HLA-B60 binding HA-1(H) and HA-1(R) peptides. In subsequent analyses, dendritic cells pulsed with the nonameric HA-1(R) peptide did not induce CTLs that recognize the natural HLA-B60/HA-1(R) ligand. In contrast, dendritic cells pulsed with the nonameric HA-1(H) peptide induced IFN-gamma-secreting T cells specific for the natural HLA-B60/HA-1(H) ligand in three HLA-B60(+) HA-1(RR) individuals, demonstrating the immunogenicity of the HLA-B60/HA-1(H) ligand. In conclusion, this study shows a novel HLA-B60-restricted T cell epitope of the minor histocompatibility Ag HA-1 locus.     

Divergent role for TNF-alpha in IFN-gamma-induced killing of Toxoplasma gondii and Salmonella typhimurium contributes to selective susceptibility of patients with partial IFN-gamma receptor 1 deficiency

Patients with defects in IFN-gamma- or IL-12-mediated immunity are susceptible to infections with Salmonella and non-tuberculous mycobacteria, but rarely suffer from infections with other intracellular pathogens such as Toxoplasma gondii. Here we describe macrophage and T cell function in eight individuals with partial IFN-gamma receptor 1 (IFN-gammaR1) deficiency due to a mutation that results in elevated cell surface expression of a truncated IFN-gammaR1 receptor that lacks the intracellular domain. We show that various effector mechanisms dependent on IFN-gammaR signaling are affected to different extents. Whereas TNF-alpha production was normally up-regulated in response to IFN-gamma, IL-12 production and CD64 up-regulation were strongly reduced, and IFN-gamma-mediated killing of the intracellular pathogens Salmonella typhimurium and T. gondii was completely abrogated in patient's macrophages. Since these patients suffer selectively from infections with non-tuberculous mycobacteria and Salmonella, but not T. gondii, despite sero-immunity in six of eight patients, which indicates previous contact with this pathogen, we next studied the role of TNF-alpha as a possible immune compensatory mechanism. IFN-gamma-induced killing of T. gondii appeared to be partially mediated by TNF-alpha, and addition of TNF-alpha could compensate for the abrogated killing of T. gondii in the patient's macrophages. In contrast, IFN-gamma-mediated killing of S. typhimurium appeared to be independent of TNF-alpha. We propose that the divergent role of TNF-alpha in IFN-gamma-induced killing of T. gondii and S. typhimurium may at least partially explain the highly selective susceptibility of patients.     

The Role of auxin,pH, and stress in the activation of embryogenic cell division in leaf protoplast-derived cells of alfalfa

Culturing leaf protoplast-derived cells of the embryogenic alfalfa (Medicago sativa subsp. varia A2) genotype in the presence of low (1 microM) or high (10 microM) 2, 4-dichlorophenoxyacetic acid (2,4-D) concentrations results in different cell types. Cells exposed to high 2,4-D concentration remain small with dense cytoplasm and can develop into proembryogenic cell clusters, whereas protoplasts cultured at low auxin concentration elongate and subsequently die or form undifferentiated cell colonies. Fe stress applied at nonlethal concentrations (1 mM) in the presence of 1 microM 2,4-D also resulted in the development of the embryogenic cell type. Although cytoplasmic alkalinization was detected during cell activation of both types, embryogenic cells could be characterized by earlier cell division, a more alkalic vacuolar pH, and nonfunctional chloroplasts as compared with the elongated, nonembryogenic cells. Buffering of the 10 microM 2,4-D-containing culture medium by 10 mM 2-(N-morpholino)ethanesulfonic acid delayed cell division and resulted in nonembryogenic cell-type formation. The level of endogenous indoleacetic acid (IAA) increased transiently in all protoplast cultures during the first 4 to 5 d, but an earlier peak of IAA accumulation correlated with the earlier activation of the division cycle in embryogenic-type cells. However, this IAA peak could also be delayed by buffering of the medium pH by 2-(N-morpholino)ethanesulfonic acid. Based on the above data, we propose the involvement of stress responses, endogenous auxin synthesis, and the establishment of cellular pH gradients in the formation of the embryogenic cell type.     

Biochemical, molecular and structural analysis of multiple thaumatin-like proteins from the elderberry tree (Sambucus nigra L.)

Thaumatin-like proteins (TLPs) were isolated and characterized from fruits and leaves of elderberry (Sambucus nigra) and their corresponding genes cloned. In addition, the developmental regulation and induction of the different TLPs was followed in some detail. Ripening berries accumulated a fruit-specific TLP during the final stages of maturation. This fruit-specific TLP had no antifungal activity and was devoid of beta-glucanase activity. Leaves constitutively expressed a TLP that closely resembled the fruit-specific homologue. Treatment with jasmonate methyl ester induced two additional TLPs in leaves but did not induce or enhance the expression of TLPs in immature berries. In contrast to jasmonate methyl ester, both ethephon and garlic extract induced the expression of a TLP in unripe berries that normally do not express any TLP. Sequence analysis and molecular modeling indicated that all elderberry thaumatin-like proteins share a high sequence similarity with group-5 pathogenesis-related proteins. However, the proteins encoded by the different sequences differed from each other in isoelectric point and the distribution of the charges on the surface of the molecule.     

Bronchoalveolar lavage fluid differential cell count. How many cells should be counted?

OBJECTIVE: To investigate the number of cells to be counted in cytocentrifuged bronchoalveolar lavage (BAL) fluid preparations in order to reach a reliable enumeration of each cell type. STUDY DESIGN: A total of 136 BAL fluid samples for patients with suspected pneumonia or interstitial lung disease were investigated. Differential cell counts were performed on May-Grünwald-Giemsa-stained cytocentrifuged preparations by 2 observers, each differentiating 500 cells. Reliability for the enumeration of each cell type was expressed as phi value, as calculated in generalizability theory. RESULTS: For polymorphonuclear neutrophils (PMNs), alveolar macrophages, lymphocytes and eosinophils, an acceptable phi value of > or = .95 was reached at a count of 300 cells by 1 observer. Mast cells reached a phi value of only .674 at a count of 500 cells by 1 observer, precluding a reliable count. At a count of 500 cells by 1 observer, squamous epithelial cells, bronchial epithelial cells and plasma cells displayed phi values of .868, .903 and .816, respectively. CONCLUSION: At a count of 300 cells, PMNs, alveolar macrophages, lymphocytes and eosinophils are reliably enumerated in cytocentrifuged BAL fluid samples.     

Functional expression of murine LRP1 requires correction of Lrp1 cDNA sequences

Here, we describe the reconstruction of a functional 14 kbp full-length murine Lrp1 cDNA from overlapping partial cDNAs, which were described before [Biochim. Biophys. Acta 1173 (1993) 71]. The reconstructed full-length cDNA needed sequence correction (by mutagenesis) due to nucleotide errors present in the underlying partial cDNAs. These mistakes compromised the proteolytical maturation of the LRP precursor (4545 aa) into its alpha- and beta-subunits. To identify these mistakes initially, detailed sequence analyses and comparison of genomic and cDNA sequences of different murine strains proved to be necessary to obtain correct wild-type sequences. Comparison of Lrp1 cDNA sequences of CBA mice with Lrp1 genomic exon sequences of 129P3/J mice (like in man 89 exons) revealed only 24 nucleotide differences within about 14.8 kbp. Only 1 out of 23 nucleotide differences in the protein coding region affected an amino acid residue: Thr versus Ala at amino acid residue position 2642 in 129P3/J and CBA, respectively. After correction by mutagenesis, both a 129P3/J and a CBA-based version of a full-length wild-type Lrp1 cDNA were functionally expressed in an LRP-deficient mutant CHO cell line. Transient expression showed the expected maturation of the LRP precursor into its two subunits. Furthermore, stable transfection restored the sensitivity to exposure to Pseudomonas aeruginosa toxin A (PEA). Since LRP is the unique receptor for this toxin, this indicates that the toxin could enter the cells after binding to and endocytosis by its genuine receptor. This murine LRP expression system will be instrumental in future experimental dissection of this multifunctional receptor.     

Optimization of an ovine antibody-secreting cell assay for detection of antigen-specific immunoglobulin production in peripheral blood leukocytes

Enumeration of antibody-secreting cells in peripheral blood by enzyme-linked immunospot (ELISPOT) has been used in human studies to detect antigen-specific antibody production at mucosal tissue sites. An alternative assay for detecting and quantitating antigen-specific antibody responses involves culturing circulating peripheral blood antibody-secreting cells and quantitating specific antibody production in culture supernatant by ELISA. In the present study, antigen-specific peripheral blood lymphocytes were isolated from subcutaneously immunized sheep and the parameters for maximizing in vitro antibody production by in vivo-induced antibody-secreting cells optimized for this species. Maximum antibody-secreting cell responses were observed in peripheral blood collected four days after antigen challenge. The addition of lipopolysaccharide and antisheep immunoglobulin had no effect on in vitro antibody secretion by blood antibody-secreting cells, while the effects of pokeweed mitogen were highly variable. However, the combination of anti-Ig and recombinant ovine interleukin-6 to peripheral blood lymphocyte cultures was found to markedly and consistently enhance specific antibody production. In unstimulated cultures, the optimal peripheral blood lymphocyte concentration for generating the greatest antibody responses was 5.0 x 107 cells per mL, but in cultures stimulated with recombinant ovine interleukin-6/antisheep immunoglobulin, the optimal cell concentration was lowered to approximately 1.0 x 107 cells per mL. In vitro, peak immunoglobulin production was usually achieved by day one in unstimulated cultures. In recombinant ovine interleukin-6/antisheep immunoglobulin-stimulated cultures, antibody levels were similar to unstimulated cultures by day one, however, the levels continued to rise during incubation to reach a maximum between days four and five of incubation. This optimized antibody-secreting cell culture assay is amenable for increasing the sensitivity and reducing the cell numbers required for quantitating antigen-specific antibody induction in large-scale immunization trials in sheep and other large animal species.     

Deficiency in the organic cation transporters 1 and 2 (Oct1/Oct2 [Slc22a1/Slc22a2]) in mice abolishes renal secretion of organic cations

The polyspecific organic cation transporters 1 and 2 (Oct1 and -2) transport a broad range of substrates, including drugs, toxins, and endogenous compounds. Their strategic localization in the basolateral membrane of epithelial cells in the liver, intestine (Oct1), and kidney (Oct1 and Oct2) suggests that they play an essential role in removing noxious compounds from the body. We previously showed that in Oct1(-/-) mice, the hepatic uptake and intestinal excretion of organic cations are greatly reduced. Since Oct1 and Oct2 have extensively overlapping substrate specificities, they might be functionally redundant. To investigate the pharmacologic and physiologic roles of these proteins, we generated Oct2 single-knockout and Oct1/2 double-knockout mice. Oct2(-/-) and Oct1/2(-/-) mice are viable and fertile and display no obvious phenotypic abnormalities. Absence of Oct2 in itself had little effect on the pharmacokinetics of tetraethylammonium (TEA), but in Oct1/2(-/-) mice, renal secretion of this compound was completely abolished, leaving only glomerular filtration as a TEA clearance mechanism. As a consequence, levels of TEA were substantially increased in the plasma of Oct1/2(-/-) mice. This study shows that Oct1 and Oct2 together are essential for renal secretion of (small) organic cations. A deficiency in these proteins may thus result in increased drug sensitivity and toxicity.     

Detailed glycan analysis of serum glycoproteins of patients with congenital disorders of glycosylation indicates the specific defective glycan processing step and provides an insight into pathogenesis

The fundamental importance of correct protein glycosylation is abundantly clear in a group of diseases known as congenital disorders of glycosylation (CDGs). In these diseases, many biological functions are compromised, giving rise to a wide range of severe clinical conditions. By performing detailed analyses of the total serum glycoproteins as well as isolated transferrin and IgG, we have directly correlated aberrant glycosylation with a faulty glycosylation processing step. In one patient the complete absence of complex type sugars was consistent with ablation of GlcNAcTase II activity. In another CDG type II patient, the identification of specific hybrid sugars suggested that the defective processing step was cell type-specific and involved the mannosidase III pathway. In each case, complementary serum proteome analyses revealed significant changes in some 31 glycoproteins, including components of the complement system. This biochemical approach to charting diseases that involve alterations in glycan processing provides a rapid indicator of the nature, severity, and cell type specificity of the suboptimal glycan processing steps; allows links to genetic mutations; indicates the expression levels of proteins; and gives insight into the pathways affected in the disease process.     

cAMP-sensitive endocytic trafficking in A6 epithelia

Blocker-induced noise analysis and laser scanning confocalmicroscopy were used to test the idea that cAMP-mediated vesicle exocytosis/endocytosis may be a mechanism for regulation of functional epithelial Na⁺ channels (ENaCs) at apical membranes of A6epithelia. After forskolin stimulation of Na⁺ transport andlabeling apical membranes with the fluorescent dyeN-(3-triethylammoniumpropyl)4-(6-4 diethylaminophenyl)hexatrienyl pyridinium dibromide (FM 4-64), ENaC densities(N_T) decreased exponentially (time constant~20 min) from mean values of 320 to 98 channels/cell within 55 minduring washout of forskolin. Two populations of apical membrane-labeledvesicles appeared in the cytosol within 55 min, reaching mean valuesnear 18 vesicles/cell, compared with five vesicles per cell in control,unstimulated tissues. The majority of cAMP-dependent endocytosedvesicles remained within a few micrometers of the apical membranes forthe duration of the experiments. A minority of vesicles migrated to >5µm below the apical membrane. Because steady states require identicalrates of endocytosis and exocytosis, and because forskolin increased endocytic rates by fivefold or more, cAMP/protein kinase A acts kinetically not only to increase rates of cycling of vesicles at theapical membranes, but also principally to increase exocytic rates.These observations are consistent with and support, but do not prove,that vesicle trafficking is a mechanism for cAMP-mediated regulation ofapical membrane channel densities in A6 epithelia.