Search PubMed⌕ Search

Biomedical subjects

C Heusser

Publications and source records attributed to C Heusser.

At least 55 records · Page 3Linked to original sources
PubMed1990

Localization of gamma/delta T cells to the intestinal epithelium is independent of normal microbial colonization.

Using monoclonal antibodies identifying all gamma/delta and alpha/beta T cell receptors in cytofluorometric analysis, we have compared the composition of intestinal intraepithelial lymphocytes (i-IEL) in euthymic and athymic germ-free (GF) and conventional (SPF) mice. The results show a marked influence of microbial colonization in the numbers of single-positive (CD4+ or CD8+) alpha/beta i-IEL, but little effect in the pool size or characteristics of gamma/delta i-IEL. In young athymic mice, virtually no alpha/beta i-IEL are detected, while considerable numbers of gamma/delta i-IEL remain, though reduced in GF animals.

Animals↗
PubMed1989

Generation of a recombinant mouse-human chimaeric monoclonal antibody directed against human carcinoembryonic antigen.

A procedure was devised for the identification and specific cloning of functionally rearranged variable region immunoglobulin (Ig) gene segments from genomic DNA of a murine hybridoma cell line which produces a high-affinity monoclonal antibody (MAb) directed against human carcinoembryonic antigen (CEA). The cloned, functionally-rearranged murine Ig H-chain and L-chain variable region gene segments were incorporated into plasmid vectors capable of directing the expression of a chimaeric mouse-human antibody molecule with human (gamma 4, kappa) constant region sequences. Expression plasmids were transfected into a mouse myeloma cell line by electroporation and transfectomas secreting functional chimaeric antibody selected. Chimaeric antibody generated by transfectomas was analysed and shown to compete effectively with its murine counterpart for binding to the CEA epitope, and to have an equivalent antigen-binding affinity. This anti-CEA recombinant antibody should find application in in vivo diagnosis by immunoscintigraphy of human colonic carcinoma, and possibly also in therapy of the disease, overcoming some of the difficulties associated with the repeated use of non-human immunoglobulins in human patients.

Animals↗
PubMed1989

Pure human inactive renin. Evidence that native inactive renin is prorenin.

To clarify contradicting observations on the identity of inactive renin and prorenin, inactive renin was completely purified from native human chorion laeve and the culture medium of human chorion cells. A 720,000-fold purification with 14% recovery was achieved from chorion laeve in 6 steps, including immunoaffinity chromatography on a monoclonal antibody to human renin coupled to Protein A-Sepharose CL-4B. A 3,100-fold purification with 40% recovery was achieved from chorion culture medium in 4 steps, including immunoaffinity chromatography. Inactive renin purified from the two different sources migrated as a single protein band with the same molecular weight of 47,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and consisted of multiple components that could be resolved by isoelectric focusing. Both had the same pI values which shifted downward upon activation by trypsin; however, relative peak heights were different between the two preparations. The purified inactive renin from chorion laeve was completely inactive and did not bind to pepstatin-aminohexyl-Sepharose; however, that from chorion culture medium was partially active and completely bound to the pepstatin gel, indicating that each molecule is partially activated. Trypsin-activated inactive renins from both sources were identical with human renal renin in terms of pH optimum and Km. Specific activities of trypsin-activated inactive renin from chorion laeve and chorion culture medium were 529 Goldblatt units/mg of protein and 449 Goldblatt units/mg of protein, respectively. Amino acid sequence analysis of both of the purified inactive renin preparations demonstrated a leucine residue at the amino terminus. The sequence of 11 additional amino acids was identical in both and agreed with that predicted from the base sequence of the renin gene. These findings indicate that preprorenin is converted to prorenin following removal of a 23-amino acid signal peptide and that the native inactive renin, whose amino acid sequence commences with Leu-Pro-Thr..., is prorenin.

Amino Acid Sequence↗
PubMed1989

Phosphorylcholine acts as a Ca2+-dependent receptor molecule for lymphocyte perforin.

Large granular lymphocytes and cytolytic T-lymphocytes (CTL) contain numerous cytoplasmic granules thought to be responsible, at least in part, for the cytolytic activity of these effector cells. Isolated granules are lytic for a variety of target cells and the granule proteins are specifically released upon target-cell interaction. Major proteins in mouse CTL granules are a family of seven serine proteases designated granzymes A to G, and a pore-forming protein called perforin (cytolysin). Purified perforin is cytolytic in the presence of Ca2+ and shows ultrastructural, immunological and amino-acid sequence similarities to complement component C9. Despite these similarities, perforin and C9 are clearly distinct in their mode of target-cell recognition. Whereas C9 insertion is absolutely dependent on a receptor moiety assembled from the complement proteins C5b, C6, C7, and C8 on the target-cell membrane, no requirement for a receptor molecule has been reported for perforin. Here, we demonstrate that phosphorylcholine acts as a specific, Ca2+-dependent receptor molecule for perforin.

Animals↗
PubMed1989

Production of human antibodies to bee venom phospholipase A2 in vitro.

Phospholipase A2 (PLA) is the major antigen of bee venom. Whereas individuals frequently stung by bees, such as bee keepers, show high levels of IgG4 anti-PLA antibodies in serum, most patients sensitive to bee venom possess increased IgE anti-PLA. We have established a culture system by which anti-PLA antibodies can be induced in vitro. Peripheral blood mononuclear cells were stimulated in a first step with PLA and/or pokeweed mitogen (PWM). After 3 days of culture the cells were washed and further incubated with fresh medium. Anti-PLA antibodies were estimated by an enzyme-linked immunosorbent assay (ELISA) and anti-PLA antibody secreting cells were counted by means of an ELISA plaque assay. Cells from bee keepers, but not those from normal donors, produced anti-PLA IgG in vitro. The isotype pattern of anti-PLA antibodies produced in vitro was identical to that found in serum of the respective donor. Anti-PLA IgM antibody-secreting cells developed at low frequencies in both bee keepers and normal donors whereas PLA-specific IgE could not be detected. The formation of anti-PLA IgG was suppressed by high amounts of antigen, while the IgM response was not affected. We conclude that PWM-induced antibodies reflect the in vivo situation of the donors and that anti-PLA IgG and IgM are regulated by different pathways and mechanisms.

Bee Venoms↗
PubMed1989

Regulation of IgG1 and IgE synthesis by interleukin 4 in mouse B cells.

Mouse interleukin 4 (IL-4) has been shown to act on B cells as an induction factor for Ig class switch. We studied the characteristics of IL-4-regulated Ig isotype production in lipopolysaccharide (LPS)-stimulated splenic B-cell cultures with emphasis on the comparison between the IgG1 and IgE responses. The results show that the kinetics for the appearance of IgG1 and IgE isotypes are similar, but that the dose of IL-4 required for the induction of an IgE response is 3-10 times higher than that for an IgG1 response. No requirement for T cells was found for the induction of either isotype. Pre-incubation of cells for 24 h with IL-4 alone was sufficient to induce an IgG1 response when cells were recultured with LPS from days 1 to 6. However, the simultaneous presence of both IL-4 and LPS for at least 24 h was required for a detectable IgE response. For an optimal IgE response, IL-4 needed to be present for more than 72 h in LPS-activated cultures. The possible reasons for the different regulation of IgG1 and IgE responses are discussed.

Animals↗
PubMed1988

Interleukin 4 instructs uncommitted B lymphocytes to switch to IgG1 and IgE.

Mouse interleukin 4 (IL 4) is a T cell-produced lymphokine with multiple effects on different cells types of the hematopoietic lineages. IL 4 has pronounced effects on B lymphocytes, where it induces high levels of IgG1 and IgE secretion in lipopolysaccharide-stimulated cultures that would otherwise secrete predominantly IgG3 and IgG2b (of the non-IgM isotypes). An important question is how IL 4 exerts its effect. Two main possibilities exist: (a) IL 4 instructs uncommitted B lymphocytes to IgG1 and IgE production; (b) IL 4 selects and expands an already precommitted B cell. In this study we show, by the use of limiting dilution analysis, that IL 4 dramatically increases the precursor frequency of IgG1 and IgE-secreting cells with no significant effect on the clone size, clearly suggesting that IL 4 instructs uncommitted B cells to switch to IgG1 and IgE. The fraction of total Ig precursors that can switch to the two isotypes is furthermore high. The high precursor frequency for IgE obtained in the presence of IL 4 further demonstrates that IL 4 is an important modulator of IgE responses.

Animals↗
PubMed1988

Regulation of immunoglobulin isotype expression in mice by antibodies in immune complexes.

Fc-dependent regulation of humoral immune responses was investigated by immunization of BALB/c mice with immune complexes. These complexes were composed of DNP- and PC-conjugated KLH or Ficoll, and monoclonal T15 idiotype-positive anti-PC antibodies of different isotypes but indistinguishable V-region properties. Since the response to DNP was analyzed, effects due to masking of antigenic determinants by anti-PC antibodies are excluded. The responses to free and complexed antigens showed significant differences in the proportions of DNP-specific IgM, IgG1, IgG2 and IgG3 antibodies. Complexes containing the T-dependent carrier KLH elicited serum antibodies to DNP with significantly decreased IgM levels, irrespective of the isotype in the complex. Under these conditions, however, DNP-specific IgG classes were augmented to various extents, depending on the isotype in the complex. In the case of the T-independent carrier Ficoll, only complexes with IgM or IgG3 suppressed the IgM response. Moreover, immunization with complexes composed of IgM or IgG2a led to a significant decrease of DNP-specific IgG1. In contrast to changes induced by antibodies bound to the T-dependent antigen, immunization with T-independent complexes did not enhance the production of any of the immunoglobulin isotypes.

Animals↗
PubMed1987

Human renin biosynthesis and secretion in normal and ischemic kidneys.

The pathway of renin biosynthesis and secretion in normal and ischemic human kidneys has been investigated by pulse-labeling experiments. The results indicate that in normal human kidney, preprorenin is rapidly processed to 47-kDa prorenin. Microradiosequencing showed that this molecule was generated by cleavage between Gly-23 and Leu-24, yielding a 43-amino acid proregion. Analysis of prorenin secreted by the kidney tissue yielded an identical sequence, indicating that prorenin is secreted without any further proteolysis. An examination of the kinetics of processing and secretion suggested that a majority of the newly synthesized prorenin is quickly secreted, while only a small fraction is processed intracellularly to the mature renin. The differences in secretion kinetics between prorenin and mature renin and the selective inhibition of prorenin secretion by monensin suggest that they are secreted independently via two pathways: a constitutive pathway probably from the Golgi or protogranules that rapidly release prorenin and a regulated pathway that secretes mature renin from the mature granules. A comparison of the kinetics of processing between normal and ischemic tissues suggests that renal ischemia leads to an overall increase in the rate of processing of prorenin to mature renin. In addition, prolonged biosynthetic labeling of renin in the ischemic kidney yielded two smaller molecular weight immunoreactive forms suggestive of renin fragments that may be degradative products. These fragments were not detected in normal kidney tissue labeled for similar lengths of time.

Cytoplasmic Granules↗
PubMed1987

Modification of the interaction of human renin with different substrates by monoclonal antibodies.

The mechanism by which anti-renin antibody inhibits renin activity was studied by following the kinetics of the reaction with angiotensinogen or a low molecular weight synthetic substrate, tetradecapeptide (TDP). Two monoclonal antibodies (70 pM) inhibited the production of angiotensin I from angiotensinogen but they differed when hog TDP was used as a substrate. R3-47-10 partially and non-competitively inhibited, whereas R3-36-16 stimulated the activity of renin. This is in contrast to the effects of the synthetic renin inhibitor, CGP 29 287, which competitively inhibits the enzyme activity with both substrates. These antibodies probably bind to the renin molecule on the flap which protects the active cleft. Angiotensinogen may be prevented from entering the cleft due to steric hindrance from bound antibody. However TDP, because of its smaller size may still be able to reach the catalytic site. In addition R3-36-16 might freeze the flap in an open position allowing a greater turnover of TDP whereas R3-47-10 may prevent the flap from fully opening and thereby hinder the reaction of TDP with the active site.

Angiotensinogen↗
PubMed1987

Effects of chronic administration of a monoclonal antibody against human renin in the marmoset.

In this study, the hypotensive efficacy of R-3-36-16, a monoclonal antibody against human kidney renin, was investigated during chronic administration to a primate. R-3-36-16 was given by continuous intraperitoneal infusion with osmotic minipumps to normotensive marmosets fed a low-sodium diet in doses of 30 or 300 micrograms/kg/day for 14 days. The lower dose had no effect on blood pressure (BP) or plasma renin activity (PRA). After two days of treatment, the higher dose reduced PRA by 57% and lowered BP by 13 +/- 7 mm Hg. Although the hypotensive response persisted after 14 days of treatment (-17 +/- 2 mm Hg), PRA had recovered to pretreatment levels. BP gradually returned to pretreatment values in the week after stopping the treatment. There was no evidence of an immune reaction when an acute challenge dose of R-3-36-16 was given 7 weeks after stopping the chronic treatment. Thus, R-3-36-16 appears to be an effective and well-tolerated hypotensive agent during chronic administration to sodium-depleted primates. The hypotensive response does not seem to be directly related to the inhibition of renin in the plasma.

Animals↗
PubMed1986

Autonomous activation of B and T cells in antigen-free mice.

The spleen of adult antigen-free mice contains a sizable proportion (5-15%) of activated cells in all lymphocyte sets, as marked by the membrane expression of immunoglobulins, L3T4 and Lyt-2 antigens. The frequency of activated cells is very high in early post-natal life, and reaches adult levels by 6 weeks of age when it is comparable to that observed in healthy unmanipulated mice raised in conventional conditions. The effector B cell compartment is quantitatively similar in antigen-free mice and specific pathogen-free mice, but the former is deficient in isotype diversification, since IgG- and IgA-secreting cells are drastically reduced. The effector T cell compartment is slightly reduced in number, but is equally competent in providing help or suppression of syngeneic B cells. The results indicate the existence of a compartment of the immune system displaying autonomous self-determined activity which is predominant early in life. This compartment, physically localized to the spleen, appears to be distinct from an antigen-dependent compartment which is essential for the development of peripheral lymphoid organs draining sites of "natural" environmental immunization.

Animals↗
PubMed1986

Generation of agammaglobulinaemic mice by prenatal and postnatal exposure to polyclonal or monoclonal anti-IgM antibodies.

Improved experimental conditions are described for the treatment of mice with anti-IgM antibody, which subsequently lead to B-cell deficiency and agammaglobulinaemia. Antibody transmitted via maternal milk alone was found to be more efficient in inducing suppression of serum immunoglobulin isotypes than prenatal transmission or postnatal intraperitoneal injections alone. However, the combined treatment by all three routes of exposure to anti-IgM resulted in total B-cell suppression associated with undetectable levels of all serum immunoglobulin isotypes. Furthermore, suppression of B-cell generation was also achieved with a rat monoclonal mu-specific antibody. The possibility of generating agammaglobulinaemic mice may be useful for investigating the influence of B cells on the generation of T-cell reactivities, and for analysing the effects of monoclonal antibodies in the absence of interfering serum immunoglobulin.

Agammaglobulinemia↗
PubMed1986

Monoclonal antibodies against human renin. Blood pressure effects in the marmoset.

The in vivo effects of two anti-human renin monoclonal antibodies with a high binding affinity for primate renin were studied in conscious, volume-depleted marmosets. These antibodies, R-3-17-7 and R-3-36-16, both have high binding activity for renin, but only R-3-36-16 inhibits the enzymatic activity of renin in vitro. In vivo, R-3-17-7 did not affect blood pressure after intravenous injection of doses up to 100 micrograms/kg, although plasma renin activity was partially reduced. In contrast, R-3-36-16 induced a reduction in blood pressure and an inhibition of plasma renin activity at a threshold dose of 3 micrograms/kg. The maximum fall in blood pressure and complete inhibition of plasma renin activity were observed after R-3-36-16, 10 micrograms/kg; these effects persisted for up to 2 hours. Pretreatment with a converting enzyme inhibitor or nephrectomy prevented the hypotensive effects of R-3-36-16. Conversely, pretreatment with R-3-36-16 prevented the hypotensive effects of a converting enzyme inhibitor. These findings indicate that the hypotensive response induced by R-3-36-16 is due entirely to blockade of the renin-angiotensin system. Thus, R-3-36-16 appears to be a specific, potent, and long-acting inhibitor of primate renin. Such monoclonal antibodies provide interesting tools for studying the effects of acute and chronic renin blockade.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1985

Comparison of different drug interference with the renin-angiotensin system.

The hypotensive effects of inhibitors of renin or converting-enzyme (CE) were compared in normotensive sodium-depleted marmosets. Renin was inhibited by an antiserum or a monoclonal antibody against human kidney renin or by peptidic renin inhibitors. The fall in blood pressure after the administration of renin antibodies or inhibitors was accompanied by complete inhibition of plasma renin activity. Antiserum and monoclonal antibody induced a hypotensive response of similar magnitude as peptidic renin inhibitors but had a longer duration of action. Teprotide was used as a CE-inhibitor. Inhibition of renin or CE lowered blood pressure but did not affect heart rate. The magnitude of the hypotensive effect was comparable after renin- or CE-inhibition and depended on the pretreatment plasma renin activity. Inhibition of renin prevented the hypotensive response to inhibition of CE and vice versa. The results of these comparative studies suggest that, in states of sodium depletion, the acute hypotensive effects of renin- or CE-inhibitors are entirely due to their interference with the renin-angiotensin system.

Angiotensin-Converting Enzyme Inhibitors↗