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PubMed2002

Gastro-allergic anisakiasis as a consequence of simultaneous primary and secondary immune response.

Gastro-allergic anisakiasis has been reported as an entity in which an acute parasitism by Anisakis simplex is accompanied by an immunoglobulin (Ig)E-mediated systemic allergic reaction. Serum samples were obtained from 24 patients within 24 h after the onset of symptoms (day 0) and after 1 month (day 30) and in 13 patients after 6 months. Total IgE was assessed by the Imx method. Specific IgE was assessed by CAP-FEIA. Specific IgM, IgG, IgG4 and IgA antibodies were assessed by enzyme-linked immunosorbent assay against crude extract (CE) and excretory-secretory products (ESP). IgE immunoblotting (IB) was directed against CE or ESP (day 0 and day 30). We found a rise of total IgE, specific IgE, number of bands in IgE-IB, IgG and IgG4 between day 0 and day 30 with a fall to near basal levels after 6 months. IgM levels were highest at day 0, falling over the next 6 months and IgA levels remained almost unchanged. Correlation studies revealed a parallel stimulation of nearly all Ig isotypes, except IgM anti-ESP, whose antibody levels correlated negatively with specific IgG levels. We found an extension of the IgE antibody repertoire in IB. We conclude that the allergic IgE-mediated reaction in the course of gastro-allergic anisakiasis involves a parallel secondary Th2 type memory response and a primary immunologic stimulation of both Th2 and Th1 lymphocyte subsets against previously unrecognized antigens.

Animals↗
PubMed1987

Agents that decrease gonadotropin-releasing hormone (GnRH) receptor internalization do not inhibit GnRH-mediated gonadotrope desensitization.

Exposure of pituitary cell cultures to GnRH causes gonadotropin release, receptor capping, internalization, and loss as well as altered responsiveness of the target cell. In the present study, the relationship between loss of gonadotrope secretory responsiveness to GnRH (desensitization) and internalization of the GnRH-receptor complex was examined. Pituitary cell cultures were pretreated (30 min) with vinblastine (100 microM, a concentration that prevents measurable receptor internalization) or with medium containing carrier only, incubated with 10(-7) M GnRH (a desensitizing concentration) with or without vinblastine or with medium alone for 60 min, and finally washed and rechallenged for 3 h with increasing concentrations of GnRH to assess the degree of desensitization as determined by LH release. Results indicate that vinblastine had no measurable effect on the ability of GnRH to stimulate LH release or desensitize the cells. In a second series of studies, a GnRH analog (D-Lys6-GnRH) was immobilized to a cross-linked agarose matrix. The covalent link was shown to be stable by biological, immunological, and physical criteria. This product bound to the GnRH receptor and provoked LH release, but was not internalized, as determined by GnRH receptor binding assays. Cultured cells were treated with either 10(-9) M free analog or an equivalent concentration of coupled analog (as measured by LH release) for 3 h. Cells were washed, then rechallenged with GnRH to assess desensitization. Both the free and coupled analogs provoked an equivalent degree of desensitization. While a significant degree of desensitization also occurred in the presence of 3 mM EGTA (conditions that totally inhibited GnRH-stimulated LH release), the loss of responsiveness was not as great as in the absence of EGTA, indicating that partial depletion of available LH may play a role in GnRH-stimulated gonadotrope desensitization. The present findings suggest that GnRH receptor internalization and LH release can be uncoupled and that loss of the GnRH receptor by internalization is not a sufficient explanation for GnRH-mediated desensitization of the gonadotrope.

Animals↗
PubMed2005

Immunosynapse formation coincides with rapid activation of NK cells by syngeneic T cells and correlates with clustering of MHC class I.

T cells cultured for 3 h with antigen-presenting cells (APCs) stimulated syngeneic IL-2-activated NK cells as measured via a standard chromium-release assay. Discrete caps containing both TCR and MHC-I had formed on the surface of these activated T cells. When conjugates were formed between NK cells and these activated T cells, >80% of the contact sites were in the MHC-I(dim) region outside the TCR-MHC-I cap. Stimulation with phorbol myristate acetate plus Ionomycin, which bypasses the need for cell surface events during activation, did not induce either cap formation or NK cell activation. Further, the addition of the protein transport inhibitor Brefeldin A did not block activation of NK cells. MHC-I is the major inhibitory ligand recognized by NK cells. One possible mechanism for the activation of NK cells by TCR-MHC-I-capped T cells is that aggregation of MHC-I into one region leaves the remaining T cell surface denuded of ligands for NK-inhibitory receptors. As a test of this hypothesis, we aggregated MHC-I on T cells with plate-bound anti-MHC-I mAb. This treatment conferred upon the T cells the capacity to activate NK cells, suggesting that MHC-I clustering could contribute to the observed phenomenon.

Animals↗
PubMed1999

Molecular cloning and characterization of a birch pollen minor allergen, Bet v 5, belonging to a family of isoflavone reductase-related proteins.

BACKGROUND: Birch pollen is a major cause of pollinosis and is responsible for cross-reactive oral allergies to fruits, nuts, and vegetables. The major allergen, Bet v 1, has been extensively characterized, and 3 minor allergens, Bet v 2, Bet v 3, and Bet v 4, have been cloned and sequenced. Recently, another birch pollen protein with an apparent mass of 35 kd was described as a new IgE-binding protein in birch pollen with cross-reacting homologues in plant foods. OBJECTIVE: The aim of this study was to determine the primary structure of the 35-kd birch pollen allergen and to investigate its immunologic properties. METHODS: On the basis of a known complementary DNA fragment, a PCR strategy was applied to obtain the full-length nucleotide sequence of the coding region. The protein was expressed as His-Tag fusion protein in Escherichia coli and purified by Ni-chelate affinity chromatography. Nonfusion protein was obtained by cyanogen bromide treatment of the fusion protein. IgE-binding characteristics and potential allergenicity were investigated by immunoblot, immunoblot inhibition analysis, rat basophil leukemia-cell mediator release assay, and basophil histamine release and compared with those of natural (n) Bet v 5, recombinant (r)Bet v 1, and rBet v 2. RESULTS: Recombinant Bet v 5 has a mass of 33 kd, an isoelectric point of 9.0, and sequence identity of 60% to 80% to isoflavone reductase homologue proteins from various plants. On immunoblots the recombinant Bet v 5 bound IgE from 9 (32%) of 28 sera from patients allergic to birch pollen with a CAP class of at least 3; Bet v 1 was detected by 89% of these patients. IgE immunoblot and inhibition experiments showed that nBet v 5 and rBet v 5 shared identical epitopes. A rabbit antiserum raised against pea isoflavone reductase and patients' IgE reacted with Bet v 5 and proteins of similar size in several vegetable foods, including exotic fruits. A similar reaction pattern was obtained with 2 Bet v 5-specific mAbs. Furthermore, Bet v 5 triggered a dose-dependent mediator release from rat basophil leukemia 2H3 cells passively sensitized with murine anti-birch pollen IgE and from basophils of a Bet v 5-reactive subject with birch pollen allergy. In contrast, no mediator release could be induced from basophils of a subject who was monosensitized to Bet v 1. CONCLUSIONS: This 33-kd protein, designated as Bet v 5, is a new minor allergen in birch pollen and may be responsible for pollen-related oral allergy to specific foods in a minority of patients with birch pollen allergy. Amino acid sequence comparison and immunoreactivity to anti-isoflavone reductase serum indicate that Bet v 5 is related to isoflavone reductase, a protein family that is involved in plant defense reactions.

Allergens↗
PubMed2001

Maitake extracts and their therapeutic potential.

Maitake (Grifola frondosa) is the Japanese name for an edible fungus with a large fruiting body characterized by overlapping caps. It is a premier culinary as well as medicinal mushroom. Maitake is increasingly being recognized as a potent source of polysaccharide compounds with dramatic health-promoting potential. The most recent development is the MD-fraction, a proprietary maitake extract its Japanese inventors consider to be a notable advance upon the preceding D-fraction. The D-fraction, the MD-fraction, and other extracts, often in combination with whole maitake powder, have shown particular promise as immunomodulating agents, and as an adjunct to cancer and HIV therapy. They may also provide some benefit in the treatment of hyperlipidemia, hypertension, and hepatitis.

Adjuvants, Immunologic↗
PubMed1999

[A new case of subcutaneous dirofilariasis].

Authors describe another case of subcutaneous dirofilariasis due to Dirofilaria (Nochtiella) repens in France. A 26-year-old woman was infected while on vacation in Cap d'Agde on the Mediterranean coast. The patient presented with a subcutaneous nodule in the right subclavicular region. Examination of the nodule after surgical excision revealed the presence of a worm identified as an immature female Dirofilaria repens. Dirofilariasis is a rare anthroponotic disease encountered only in the Old World, particularly in Southeastern France including Corsica which has the second highest number of reported cases after Italy. Since man is a dead-end for the parasite, Dirofilaria repens does not mature and hence most human infections present as isolated subcutaneous nodules. Nodules are usually located in areas exposed to bites by the dipteres, i.e. the face (46 p. 100 of cases reported in the world) and the periocular and palpebral region (30 p. 100). Diagnosis is based mainly on morphological examination of the worm after surgical excision. However promising results in diagnosis of ocular and visceral forms of Dirofilaria repens and understanding of helminthiasis have been achieved thanks to progress in immunological techniques, i.e., ELISA and western blot, and DNA analysis based on polymerase chain reaction.

Adult↗
PubMed1987

Electron spin resonance spectroscopy in the study of lymphoid cell receptors.

ESR spectroscopy is a sensitive method which can be used to monitor a wide range of changes in and near the plasma membranes of lymphoid cells during such events as ligand-induced receptor patching and capping, activation and endocytosis and phagocytosis. The advantages of the technique are rapidity, sensitivity, small sample size (10(6)-10(7) cells), and nondestructive nature. Spin labels that are attached to a range of intrinsic and extrinsic molecules give information about the fluidity and polarity of the environment in which they are located. Because of the occurrence of interaction when probes are sequestered in restricted regions of the membrane, ESR spectroscopy is also a valuable technique for measuring the formation of domains in the cell membrane.

Cell Membrane↗
PubMed1992

Presynaptic histamine H1 and H3 receptors modulate sympathetic ganglionic synaptic transmission in the guinea-pig.

1. To study the effects of histamine on the efficacy of sympathetic ganglionic synaptic transmission, extracellular recordings of the postganglionic compound action potential (CAP) and intracellular recordings of excitatory postsynaptic potentials (EPSPs) elicited by preganglionic electrical stimulation were obtained from isolated guinea-pig superior cervical ganglia (SCG). 2. In different preparations, superfusion with histamine (0.1-100 microM) either potentiated or depressed the postganglionic CAP elicited by electrical stimulation of the cervical sympathetic trunk (0.2-3.0 Hz). The direction of response produced by histamine did not depend on stimulation frequency or histamine concentration; potentiation and depression both showed concentration dependence over the range of histamine concentrations tested. 3. Experiments employing a variety of histamine receptor agonists or antagonists revealed that histamine-induced potentiation of the postganglionic CAP could be attributed to histamine H1 receptor activation, and depression to H3 receptor activation. 4. Histamine similarly potentiated or depressed the intracellularly recorded EPSP. However, these opposite effects occurred at different synapses. In agreement with the studies on the postganglionic CAP, histamine H1 antagonists prevented histamine-induced potentiation of the EPSP and H3 receptor antagonists prevented histamine-induced depression. 5. Direct quantal analyses of histamine-induced synaptic potentiation and depression were implemented to determine the pre- and postsynaptic components of these effects. Quantal size was estimated by measuring the amplitude of spontaneous miniature EPSP amplitudes. Histamine-induced potentiation and depression of the evoked EPSP were found to be accompanied by increased or decreased quantal content respectively, and unchanged quantal size, providing evidence that presynaptic mechanisms were involved in mediating both effects. 6. Some guinea-pigs were actively sensitized to ovalbumin. Subsequent exposure of the isolated SCG from these animals to the sensitizing antigen produced changes in the EPSP amplitude that correlated significantly to the response produced by exogenously applied histamine at the same synapse. 7. The correspondence between the effects of specific antigen challenge and exogenous histamine on evoked EPSPs at a synapse provides evidence that endogenous histamine released during an immunological response to antigen challenge can activate histamine H1 and H3 receptors to modulate synaptic efficacy in sympathetic ganglia.

Action Potentials↗
PubMed2005

Drug hypersensitivities: which room for biological tests?

Drug allergic reactions frequently represent a serious diagnostic problem. In this paper we summarise the most relevant data published in recent years on the diagnostic reliability of the in vitro techniques in drug allergy diagnosis. The lymphocyte transformation test (LTT) offers a sensitivity of 58% in the diagnosis of late allergic reactions to betalactams and 64.5% in the immediate allergic reactions. The basophil activation test and the antigen-specific sulphidoleukotriene determination have an acceptable diagnostic reliability in muscle relaxant drug-induced reactions and in betalactam allergy. BAT sensitivity in betalactam allergy was 50.7% and its specificity 93.3%, whereas CAP had a sensitivity of 36.7% and a specificity of 83.3%, and CAST, a sensitivity of 47.7% and a specificity of 83.3%. For NSAID hypersensitivity, BAT sensitivity was 63.3% and specificity 93.3%, CAST sensitivity was 38.3% and specificity 76.6%. BAT sensitivity in metamizol allergy was 42.3% and the specificity 100% and CAP was negative in all the 17 cases in which it was performed. The joint use of BAT and CAP (specific IgE) allows diagnosis of 65.2% of the betalactam allergic patients with a specificity of 83.3%. The combined use of CAST and BAT in metamizol allergy detects 76% of the cases and 76.9% when associating the skin tests. In NSAID hypersensitivity, the joint use of BAT and CAST does not increase the diagnostic reliability of BAT alone. BAT is a non-invasive useful technique in the in vitro diagnosis of betalactam and metamizol allergy, and NSAID hypersensitivity.

Anti-Bacterial Agents↗
PubMed2002

Synaptic transfer by human gamma delta T cells stimulated with soluble or cellular antigens.

B, alpha beta T, and NK lymphocytes establish immunological synapses (IS) with their targets to enable recognition. Transfer of target cell-derived Ags together with proximal molecules onto the effector cell appears also to occur through synapses. Little is known about the molecular basis of this transfer, but it is assumed to result from Ag receptor internalization. Because human gamma delta T cells recognize soluble nonpeptidic phosphoantigens as well as tumor cells such as Daudi, it is unknown whether they establish IS with, and extract molecules from, target cells. Using flow cytometry and confocal microscopy, we show in this work that Ag-stimulated human V gamma 9/V delta 2 T cells conjugate to, and perform molecular transfer from, various tumor cell targets. The molecular transfer appears to be linked to IS establishment, evolves in a dose-dependent manner in the presence of either soluble or cellular Ag, and requires gamma delta TCR ligation, Src family kinase signaling, and participation of the actin cytoskeleton. Although CD45 exclusion characterized the IS performed by gamma delta T cells, no obvious capping of the gamma delta TCR was detected. The synaptic transfer mediated by gamma delta T cells involved target molecules unrelated to the cognate Ag and occurred independently of MHC class I expression by target cells. From these observations, we conclude that despite the particular features of gamma delta T cell activation, both synapse formation and molecular transfer of determinants belonging to target cell characterize gamma delta T cell recognition of Ags.

Antigens↗
PubMed1980

Electron-microscopic cytochemical studies on the secretory process in rat prolactin cells in primary culture.

Three aspects of the secretory process in male rat prolactin (PRL) cells grown in primary cultures for 7--14 days have been investigated by cytochemical methods. The subcellular localization of prolactin has been studied using preembedding or postembedding immunocytochemical methods after various fixatives. With the postembedding method, PRL is localized essentially in secretory granules. The maximum intensity of staining is obtained with PAF fixative. With the preembedding method, subcellular localization of the staining varies depending on the fixative. After PAF-fixation, positive staining is observed on secretory granules, ground cytoplasm, the outer face of some RER cisternae and, in a few cells, on the innermost Golgi cisternae, as well as on masses of condensing secretory material. After Ohtsuki's hypotonic fixative followed by saponin permeabilization, PRL is visualized within the totality of RER cisternae, including the perinuclear cisternae and the peripheral saccules on the cis-Golgi face. Secretory granules are unstained. Membrane traffic was investigated using the Con A-HRP indirect method as a tracer of surface saccharides. Plasma membrane, coated with Con A-HRP at 4 degrees C, is slowly internalized at 37 degrees C. This involves both randomly distributed invaginations and capping. The final step of endocytosis (1--2 hours) is located in the Golgi zone, where very few smooth membranes are stained. In contrast, a conspicuous deposit is found around the dense content of secretory granules. This suggests a recycling of internalized membrane and a transfer of Con A-HRP from the inner face of smooth cisternae to the secretory material. The internalization of Con A-HRP-coated membrane leads to an inhibition of PRL release starting after 30 minutes. This is accompanied by a marked increase of acid phosphatase activity, mostly around forming and mature secretory granules.

Acid Phosphatase↗
PubMed2006

Treatment of ADHD with French maritime pine bark extract, Pycnogenol.

Attention Deficit/Hyperactivity Disorder (ADHD) is the most common psychiatric disorder in children. Pycnogenol, an extract from the bark of the French maritime pine, consisting of phenolic acids, catechin, taxifolin and procyanidins, has shown improvement of ADHD in case reports and in an open study. Aim of the present study was to evaluate the effect of Pycnogenol on ADHD symptoms. Sixty-one children were supplemented with 1 mg/kg/day Pycnogenol or placebo over a period of 4 weeks in a randomised, placebo-controlled, doubleblind study. Patients were examined at start of trial, 1 month after treatment and 1 month after end of treatment period by standard questionnaires: CAP (Child Attention Problems) teacher rating scale, Conner's Teacher Rating Scale (CTRS), the Conner's Parent Rating Scale (CPRS) and a modified Wechsler Intelligence Scale for children. Results show that 1-month Pycnogenol administration caused a significant reduction of hyperactivity, improves attention and visual-motoric coordination and concentration of children with ADHD. In the placebo group no positive effects were found. One month after termination of Pycnogenol administration a relapse of symptoms was noted. Our results point to an option to use Pycnogenol as a natural supplement to relieve ADHD symptoms of children.

Adjuvants, Immunologic↗
PubMed1997

[Reproducibility and seasonal dependence of specific intranasal provocation tests in birch pollen allergy patients].

BACKGROUND: The intranasal allergen Provocation test (INT) is the standard procedure to verify the effect of an allergen when a nasal allergy is suspected. It may be especially useful if results from skin tests or in vitro tests conflict with those from the history. In the clinical and research setting, INT may be used to study the efficacy of different treatment modalities such as pharmacotherapy or immunotherapy. The technique of INT has not been well standardized in the past. Variations exist in planning the optimum time for testing, especially in seasonal allergies. METHODS: We examined influences of different test dates with regard to the pollen season on the result of INT. A total of 19 patients (eight females, 11 males, aged 26.1 +/- 4.8 years) with a history of at least two years of allergic rhinitis to birch pollen, positive skin prick test, and RAST (> or = CAP class II) to birch pollen. INT was performed during the winter-period after approximately six months without natural pollen exposition (V1), during the birch pollen season (V2) and six weeks after the birch pollen season (V3). Allergens were applied using a pump spray (0.1 ml) in concentrations of 10, 50, 100, 500, 1000, 5000, 10,000, 50,000, and 100,000 SQ units per ml (SQ/ml). RESULTS: The threshold concentrations were significantly lower at V2 (100 SQ/ml) and V3 (500 SQ/ml) if compared to V1 (1000 SQ/ ml). CONCLUSIONS: Seasonal influences should be taken into account when performing INT in birch pollen allergy.

Adolescent↗
PubMed2003

Leishmania-induced inhibition of macrophage antigen presentation analyzed at the single-cell level.

A number of studies have previously examined the capacity of intracellular Leishmania parasites to modulate the capacity of macrophages to process and present Ags to MHC class II-restricted CD4(+) T cells. However, the bulk culture approaches used for assessing T cell activation make interpretation of some of these studies difficult. To gain a more precise understanding of the interaction between Leishmania-infected macrophages and effector T cells, we have analyzed various parameters of T cell activation in individual macrophage-T cell conjugates. Leishmania-infected macrophages efficiently stimulate Ag-independent as well as Ag-dependent, TCR-mediated capping of cortical F-actin in DO.11 T cells. However, infected macrophages are less efficient at promoting the sustained TCR signaling necessary for reorientation of the T cell microtubule organizing center and for IFN-gamma production. A reduced ability to activate these T cell responses was not due to altered levels of surface-expressed MHC class II-peptide complexes. This study represents the first direct single-cell analysis of the impact of intracellular infection on the interaction of macrophages with T cells and serves to emphasize the subtle influence Leishmania has on APC function.

Actins↗
PubMed2005

The degree of serological sensitization to cat allergen in patients with or without cat at home.

BACKGROUND: The relationship between exposure to cat/dog in domestic environments and development of allergic sensitization to pet allergens is still controversial. OBJECTIVE: To test the role of indirect exposure to cat, we aimed to evaluate the amounts of cat specific IgE in sensitized subjects with or without cat at home. METHODS: Three hundred six adult patients with a previous diagnosis of allergic sensitization to cat allergens (by skin prick test) were enrolled for this study. Among 306 men and women sensitized to cat (and other allergens), 150 owned a cat for at least 10 years ( direct exposure) and 156 had never owned this animal (indirect exposure). An internal questionnaire specifically designed for the study was completed by the same allergists during the screening consultation: the results of skin prick tests, personal and clinical data, periods of symptoms and characteristics of cat ownership were carefully recorded. Specific IgE to cat extract was determined by the Pharmacia CAP System FEIA (Pharmacia Diagnostics, Uppsala, Sweden) and Immulite 2000 (Diagnostic Products Corporation, Los Angeles, USA) RESULTS: Although specific IgE to cat allergen were significantly higher in patients with cat at home (F = 42.77; p < 0.001), high amounts of these antibodies were found also in sera of subjects indirectly exposed to cats. DISCUSSION: The results of our study demonstrate that the degree of serological sensitization to cat allergens may be relevant also in subjects without any direct contact with cats (indirect exposure).

Air Pollution, Indoor↗
PubMed1996

Rat MHC class I peptides are immunogenic.

We postulated that indirect recognition of MHC-derived peptides might modulate the alloresponse to donor antigen. In this study, we looked at the potential of two class I peptides derived from the alpha 1 and alpha 2 regions of the DA RT1Aa molecule. Lew responder rats were immunized by varying concentrations of two 25mer peptides covering residues 56-81 and 96-120. The injections were under the footpad and were repeated on day 14. The thickness of the footpads was measured to control delayed-type hypersensitivity (DTH). The animals were sacrificed on day 16 and the splenocytes were tested in mixed lymphocyte culture as responders against DA stimulator cells and CAP third-party splenocytes. In addition, the phenotype of the cells was measured using flow cytometry with antibodies against CD4, CD8, CD5, MHC class II, CD25, CD14 and CD19. Peptide 96-120 induced strong sensitization of the Lew recipient animals at concentrations of 200-500 micrograms (n = 4). The stimulation index was 2-3 times higher than that of untreated animals. Peptide 56-81 failed to induce sensitization at the concentrations used, but surprisingly induced a concentration-dependent immunosuppression that was highest at 400 micrograms (n = 4). In proliferation experiments responder Lew rats proliferated only to peptide 56-81 in vitro.

Amino Acid Sequence↗
PubMed1984

Photoaffinity-labeled hapten-binding T-cell receptor on a suppressor T-cell hybridoma.

A T-cell hydridoma, 7C3-13-Ag6, which produces a (4-hydroxy-3-nitrophenyl)acetyl (NP)-specific suppressor T-cell factor associated with an I-J determinant, was utilized to study the hapten-binding receptor of T-cells. This hybridoma had been shown to express NP-binding receptor molecules on the cell surface with heteroclitic fine specificity for a cross-reactive hapten, (4-hydroxy-5-iodo-3-nitrophenyl) acetyl (NIP). The stoichiometric analysis of the hapten binding by 7C3-13-Ag6 cells was performed by the measurement of direct binding of highly radioactive haptens to the cell surface. The affinity constant (Ka) of the receptor for N125IP-epsilon-aminocaproic acid (N125IP-cap), as calculated from a Hill plot, was 5.75 X 10(7) M-1 [Hill coefficient (a) = 0.86; expression of receptor sites per cell = approximately 1 X 10(3) on average]. The receptor molecule was specifically affinity labeled with photoreactive nitroaryl azide derivatives of N125IP (510-570 Ci/mmole). The specificity of photoaffinity labeling was demonstrated both by competitive inhibition of labeling with NIP- or NP-cap and by differential photoaffinity labeling based on the reversibility of hapten-receptor interaction. The gel electrophoretic analysis of the photoaffinity-labeled molecule indicated that the hapten-binding receptor of 7C3-13-Ag6 has a mol. wt of 28,000 +/- 3000 and an isoelectric point of 5.6-5.7. No immunoglobulin determinants were detected on the molecule. A comparative immunoprecipitation analysis of the membrane lysate of 7C3-13-Ag6 with monoclonal anti-I-J reagents identified a separate I-J molecule of 25,000 +/- 1000 mol. wt that is distinct from the photoaffinity-labeled hapten-binding molecule.

Affinity Labels↗
PubMed1974

Antigenic modulation in vitro. I. Fate of thymus-leukemia (TL) antigen-antibody complexes following modulation of TL antigenicity from the surfaces of mouse leukemia cells and thymocytes.

The modulation or loss of thymus-leukemia (TL) antigenicity from the surfaces of mouse RADA1 leukemia cells and normal thymocytes during incubation with TL antibody in vitro at 37 degrees C was investigated by cytotoxicity, immunofluorescence, and immunoelectron microscopy. The fate of bivalent and monovalent antibody during modulation was visualized by fluorescence microscopy. Considerable antibody remained bound to the cell surface after modulation, bivalent antibody being displaced topographically into "patches" and "caps" while monovalent antibody was only slightly aggregated on the cell surface. Some antibody was internalized, presumably by pinocytosis, and was sequestered into the Golgi region of the cell. Capping usually occurred over the pole of the cell opposite from the Golgi region, which may explain the lack of extensive pinocytosis of modulating bivalent antibody. Since modulation with monovalent antibody occurs without patch or cap formation, gross topographical redistribution of TL antigen-antibody complexes is not required for modulation, although more subtle displacement of these complexes may be involved. Modulation was demonstrable by cytotoxicity with guinea pig C' but not with absorbed rabbit C', indicating that modulated TL antigens remain bound to the cell surface. A heat-labile factor in TL antiserum and in mouse serum in general is responsible for "blocking" the cytolytic interaction of guinea pig C' with modulated TL antigen-antibody complexes.

Animals↗