Asymmetry of the acetylcholine channel revealed by quaternary anesthetics.

Tissue-cultured rat myoballs were examined electrophysiologically with a suction pipette, which was used for voltage clamping and internal perfusion. The lidocaine derivative QX-314 caused a time- and membrane potentia-dependent block of acetylcholine-induced current only when applied from the extracellular membrane surface. The same compounds caused a use-dependent block of the sodium channel only from the intracellular membrane surface. These experiments demonstrate a fundamental asymmetry of the acetylcholine receptor-channel complex.

Abnormalities of polymorphonuclear leukocyte function associated with a heritable deficiency of high molecular weight surface glycoproteins (GP138): common relationship to diminished cell adherence.

Investigations of polymorphonuclear leukocyte (PMN) function were performed in a 5-yr-old white female with delayed umbilical cord separation, impaired pus formation, and a severe defect of PMN chemotaxis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated an almost total deficiency of a high molecular weight glycoprotein(s) (GP138) in the granule and membrane fractions of the patient's cells, and NaB3H4-galactose oxidase labeling demonstrated the absence of a major glycoprotein complex on the surface of her PMNs. Monoclonal antibodies (MAb) were employed in flow cytometry experiments to demonstrate that two previously characterized glycoproteins (Mo1 and LFA1) were undetectable on the surface of the patient's PMNs and monocytes. Immunoprecipitation of 125I-labeled patient cells with subunit specific MAbs confirmed that the alpha-subunits of Mo1 (155 kD) and LFA1 (177 kD) and their common beta-subunit (94 kD) were totally deficient. Functional analyses of patient PMNs demonstrated severe impairment of adherence- and adhesion-dependent cell functions including spreading, aggregation, orientation in chemotactic gradients, antibody-dependent cellular cytotoxicity, and phagocytosis of particles (Oil-Red-0-paraffin, zymosan) selectively opsonized with C3-derived ligands. Patient PMNs demonstrated a normal capacity to rosette with IgG or C3b-coated sheep erythrocytes, but rosette formation with C3bi-coated erythrocytes was profoundly diminished. Adhesion-independent functions including shape change, N-formyl-methionyl-leucyl-3H-phenylalanine binding, and O-2 generation or secretion elicited by soluble stimuli were normal. Membrane fluidity, surface charge, and microtubule assembly were also normal. These findings provide new evidence that critical PMN surface glycoproteins are required to facilitate multiple adhesion-dependent cellular functions of the inflammatory response.

Collagen cell attachment protein from rat hepatoma cells.

This paper describes the isolation and partial characterization of a collagen cell attachment protein from the spent culture medium of rat hepatoma cells. When compared with serum fibronectin, this attachment protein differed in several biochemical parameters. The hepatoma attachment protein was partially purified by adsorbing and eluting from an inorganic gel, magnesium oxide. Cell adhesive activity may routinely recovered at levels of 10 to 30%, and a 2000-fold purification was attained. The hepatoma attachment protein was shown to be sensitive to trypsin and chymotrypsin, to be heat inactivated at 61 degrees, to have a molecular weight of 58,000, to have an isoelectric point of 4.1, to show an electrophoretic mobility on cellulose acetate of approximately one-half that of fibronectin, and not to cross-react with antifibronectin antisera.

Presence of anti-La(SS-B) is associated with binding to the 13-kD carboxyl terminus of 60-kD Ro(SS-A) in systemic lupus erythematosus.

In systemic lupus erythematosus (SLE) clinical manifestations, autoantibody production, and immunogenetics are inter-related. The ability to study parts of the autoimmune response may allow a more detailed understanding of these relationships. We undertook this study to determine whether the fine specificity of the autoimmune response to 60-kD Ro(SS-A) was related to the presence of other autoantibodies. We screened 74 patients with SLE for antibodies to the carboxyl 13-kD terminal of 60-kD Ro(SS-A) (13 kD). Twenty-five sera had such antibodies. This reactivity was distinguished by the presence of not only anti-Ro(SS-A) but also other antibodies. All nine sera with Ro(SS-A) and La(SS-B) Ouchterlony immunodiffusion precipitins bound 13-kD (p = 0.01), whereas 10 of 11 sera with both anti-Ro(SS-A) and anti-La(SS-B) as determined by immunosorbent assay bound 13-kD (p = 0.002). Inhibition studies demonstrated that antibodies binding the 13-kD fragment bound the 60-kD Ro(SS-A) protein but did not bind the La(SS-B) protein. Thus, anti-La(SS-B) was found in those sera that bound epitopes within the 13-kD carboxyl terminal of 60-kD Ro(SS-A). These data suggest a structural basis by which anti-Ro(SS-A) and anti-La(SS-B) are coupled in SLE.

Human autoantibody production in the severe combined immunodeficiency (scid) mouse.

We investigated the production of autoantibodies in severe combined immunodeficient (scid) mice that received an intraperitoneal injection of peripheral blood mononuclear cells (PBMC) from patients with systemic lupus erythematosus. Mice receiving 50 x 10(6) cells consistently engrafted, as evidenced by the presence of human immunoglobulin in the hu-PBL-scid serum; though none, any one, or a combination of the autoantibody specificities found in the donor could be found in the hu-PBL-scid serum. Production of anti-Ro antibody in the hu-PBL-scid chimeric mice could be enhanced by treatment with the Ro antigen. These results indicate that not only can scid mice engrafted with PBMC from patients with SLE produce autoantibody, but also that this production can be manipulated with specific antigen.

Separation of human colostral macrophages and neutrophils on gelatin and collagen-serum substrata.

A new technique for separation of human colostral macrophages and neutrophils was developed. Macrophages attached more readily to acid soluble collagen-serum or gelatin-serum substrata than neutrophils. Most of the adherent neutrophils were removed during the first 5 minutes incubation in 3 mM EDTA, thereafter, complete detachment of macrophages followed. Neutrophils and macrophages were enriched more than 80% in nonadherent cell populations and detached cell populations, respectively. These separated colostral leukocytes retained their viability and phagocytic activities. Therefore, functional studies of these purified human colostral leukocytes are possible.

Phospholipase A2 activating protein and idiopathic inflammatory bowel disease.

BACKGROUND: Crohn's disease and ulcerative colitis are idiopathic inflammatory bowel diseases (IBD) involving synthesis of eicosanoids from arachidonic acid (AA), which is released from membrane phospholipids by phospholipase A2 (PLA2). A potentially important regulator of the production of these mediators is a protein activator of PLA2, referred to as PLA2 activating protein (PLAP). AIMS: The purpose of this investigation was to discover if PLAP values might be increased in the inflamed intestinal tissue of patients with IBD and in intestinal tissue of mice with colitis. PATIENTS: Biopsy specimens were taken from patients with ulcerative colitis and Crohn's disease undergoing diagnostic colonoscopy, and normal colonic mucosa was obtained from patients without IBD after surgical resection. METHODS: Immunocytochemistry with affinity purified antibodies to PLAP synthetic peptides was used to locate PLAP antigen in sections of intestinal biopsy specimens from IBD patients compared with that of normal intestinal tissue. Northern blot analysis with a murine [32P] labelled plap cDNA probe was performed on RNA extracted from the colons of mice fed dextran sulphate sodium (DSS) and cultured HT-29 cells exposed to lipopolysaccharide (LPS). RESULTS: PLAP antigen was localised predominantly within monocytes and granulocytes in intestinal tissue sections from IBD patients, and additional deposition of extracellular PLAP antigen was associated with blood vessels and oedema fluid in the inflamed tissues. In contrast, tissue sections from normal human intestine were devoid of PLAP reactive antigen, except for some weak cytoplasmic reaction of luminal intestinal epithelial cells. Similarly, colonic tissue from DSS treated mice contained an increased amount of PLAP antigen compared with controls. The stroma of the lamina propria of the colonic mucosa from the DSS treated mice reacted intensely with antibodies to PLAP synthetic peptides, while no reaction was observed with control mouse colons. These data were supported by northern analysis which showed that PLAP mRNA was increased in the colons of DSS treated mice and cultured HT-29 cells exposed to LPS. CONCLUSIONS: As PLAP values were increased in the intestinal mucosa of IBD patients and mice with colitis, as well as in LPS treated cultured HT-29 cells, a role was postulated for PLAP in increasing PLA2 activity, which leads to the increased synthesis of eicosanoids in intestinal tissues of patients with these inflammatory diseases.

A common autoepitope near the carboxyl terminus of the 60-kD Ro ribonucleoprotein: sequence similarity with a viral protein.

The Ro ribonucleoprotein is composed of hY RNA and a 60.7-kD peptide that is antigenic for autoantibodies produced by many patients with systemic lupus erythematosus or Sjögren's syndrome and mothers of newborns with complete congenital heart block. A major immunoreactive fragment (13 kD) of the 60-kD Ro is bound by 28 of 45 (62%) of the anti-Ro sera tested. Amino acid sequence analysis localizes this fragment to the carboxyl end of the 60-kD Ro peptide. All possible overlapping octapeptides of this 13-kD peptide of 60-kD Ro have been assessed for antigenicity. Sera that bind the 13-kD peptide fragment in immunoblot generally also bind the octapeptides of Ro spanning the sequence AIALREYRKKMDIPA (P less than 0.01). Inhibition studies with synthetic peptides and purified Ro have established specificity for reference serum antibody binding to an antigenic octapeptide, EYRKKMDI, from this region. The closely related sequence EYRKKLMD is found in the nucleocapsid protein of vesicular stomatitis virus and may portend an immunologic link to this or a related viral antigen. These results also demonstrate that despite fine specificity variation between human sera, there are recurring patterns of anti-Ro binding shared by some patients who have precipitating anti-Ro autoantibodies.

Unilateral adrenal enlargement due to Histoplasma capsulatum.

Human infection with Histoplasma capsulatum runs the gamut from asymptomatic to disseminated disease. CT-directed fine-needle aspiration of bilaterally enlarged adrenal glands has been used in diagnosing serious infections with this ubiquitous organism. Three cases have previously been reported in which H. capsulatum infection caused unilateral adrenal enlargement; this enlargement was diagnosed post-mortem. We describe three patients with unilateral adrenal enlargement due to H. capsulatum whose conditions were diagnosed antemortem. We encourage clinicians to include infection with H. capsulatum as well as other granulomatous diseases and tumors in the differential diagnosis of unilateral adrenal enlargement.

Cholera toxin induces synthesis of phospholipase A2-activating protein.

The mechanism of cholera toxin (CT)-stimulated arachidonate metabolism was evaluated. CT caused rapid in vitro synthesis of prostaglandin E2 (PGE2) in murine smooth muscle-like cells (BC3H1), reaching maximal levels within 3 to 4 min. In comparison, cyclic AMP (cAMP) levels were unchanged, and addition of dibutyryl cAMP did not affect PGE2 synthesis. CT-induced PGE2 synthesis was prevented by actinomycin D or cycloheximide, indicating a need for de novo protein synthesis. Northern blot analysis of total RNA from BC3H1 cells revealed that exposure to CT resulted in an increase in abundance of mRNA encoding phospholipase A2 (PLA2)-activating protein (PLAP). PLAP is a regulatory protein that increases the enzymatic activity of cellular PLA(2), which in turn causes increased hydrolysis of arachidonate from membrane phospholipids. Furthermore, CT evoked the accumulation of PLAP mRNA in J774 (murine monocyte/macrophage) and Caco-2 (human intestinal epithelial) cells in vitro, but the responses were more delayed than that of BC3H1 cells. A protein band of approximately 35 kDa, which corresponded to the size of PLAP, was observed in sodium dodecyl sulfate extracts of Caco-2 cells by Western blot (immunoblot) analysis using affinity-purified antibodies to PLAP synthetic peptides. Synthesis of PLAP protein was increased after 2 h of exposure to CT. Exposure of mouse intestinal loops to either CT or live Salmonella typhimurium for 3 h increased mucosal PLAP mRNA levels. The role of PLAP in CT-induced PGE2 synthesis provides an attractive explanation for the reported suppression of CT-induced intestinal secretion by inhibitors of protein synthesis.

Antigenicity of a recombinant Ro (SS-A) fusion protein.

The antigenicity of the 60-kd human Ro (SS-A) synthesized in vitro from its complementary DNA as a beta-galactosidase fusion protein (beta-gal-Ro) was evaluated by Western blotting. In this analysis, almost all the anti-Ro (SS-A)-positive sera that bound beta-gal-Ro also bound affinity-purified 60-kd human Ro (SS-A) (P less than 0.005). Three of the 27 anti-Ro (SS-A) precipitin-positive sera, however, did not show reactivity on Western blot analysis, which suggests that in some sera, antigenicity to Ro (SS-A) is destroyed by denaturation. Of the 22 sera that were reactive with beta-gal-Ro, 2 were not reactive with affinity-purified human Ro (SS-A). Two serum samples that did not react with beta-gal-Ro were also reactive with affinity-purified human Ro (SS-A). Nevertheless, except for a small percentage of Ro (SS-A) precipitin-positive sera, the frequency of antibody binding to the fusion protein was similar to the frequency of binding to the purified antigen in Western blots. Recombinant Ro (SS-A) antigen may therefore be valuable in the serologic evaluation of anti-Ro (SS-A) autoantibodies.

Immunogenetics of epitopes of the carboxyl terminus of the human 60-kD Ro autoantigen.

Systemic lupus erythematosus is associated with the presence of autoantibodies which bind several ribonucleoproteins, including Ro (or SS-A). We have explored the relationship of the HLA-DQ and T cell receptor alleles in patients producing autoantibodies binding the 13-kD carboxyl terminus fragment of the 60-kD Ro and with autoantibodies binding a peptide epitope within this fragment (amino acid residues 480-494). Antibodies binding the 13-kD fragment are more likely to be found in the sera of patients with particular DQA1 and DQB1 alleles, while antibodies binding the epitope at 480-494 are found almost exclusively in the sera of patients with a Bg/II 9.8-kb polymorphism of the T cell receptor beta gene. Meanwhile, in these same patient sera the level of autoantibodies binding the complete 60-kD Ro particle is associated with a distinct pattern of alleles at these same immunoregulatory loci. These data demonstrate that component parts of autoantibody responses may be under genetic control which can be distinguished from the HLA associations characteristic of the response to the intact, complete autoantigen.