anti-M2 Antibodies Research Articles

Sera with high levels of anti-smooth muscle and anti-mitochondrial antibodies frequently bind to cytoskeleton proteins

Using ELISA methods, 54 sera from chronic active hepatitis (CAH) patients displaying high levels of anti-smooth muscle antibodies (SMA) and 18 sera from primary biliary cirrhosis (PBC) patients with high levels of anti-M2 antibodies were examined for the presence of high antibody levels against actin, tubulin, myosin, tropomyosin, troponin, vimentin and desmin. Our results showed that: (i) in CAH with high SMA activity, increased antibody levels were found in 51.9% of sera for actin, 31.5% for myosin, 35.2% for tubulin, 34.0% for tropomyosin, 11.3% for troponin, 22.6% for vimentin and 43.4% for desmin, compared with natural antibody levels in 21 normal sera; (ii) Similar high levels of these antibodies were found in the case of PBC; (iii) in most cases, sera simultaneously bound to several antigens of the panel; and (iv) approximately 26% of the CAH sera were found to be negative with the seven antigens examined while 22% were reacted with a cytoskeleton protein (CP) other than actin. These results indicate that current opinion associating SMA with anti-actin activity in CAH is confirmed for only 50% of cases and that although a good correlation between SMA and anti-CP antibodies can be obtained, there is still a significant percentage of SMA for which the putative antigen recognized needs to be determined.

Importância da interação entre a integrina Mac-1 dos leucócitos e a glicoproteína Iba das plaquetas para o recrutamento de leucócitos pelas plaquetas e para a resposta inflamatória à lesão vascular

To assess the importance of the interaction between leukocyte integrin Mac-1 (a Mb 2) and platelet glycoprotein (GP) Ib-a for leukocyte recruitment after vascular injury and the effect of the neutralization of the Mac-1-GPIba interaction on cell proliferation and the neointimal hyperplasia triggered by the vascular injury. A peptide called M2 or anti-M2 antibody was developed to block the Mac-1-GPIba interaction. This peptide was injected and compared to a control-peptide in C57B1/6J mice submitted to vascular injury of the femoral artery with a guide wire. One, five or 28 days after the vascular injury, the femoral arteries were removed for morphometric and immunohistochemical analyses. The blocking of the Mac-1-GPIba interaction promoted a statistically significant reduction in the number of leukocytes in the neointimal layer on the first day after the vascular injury (control: 7.9+/-5.0% of the cell total versus anti-M2: 2.0+/-1.6%, p=0.021), as well as determined a statistically significant decrease in leukocyte accumulation in the neointimal layer on days 5 and 28 (control: 42.3+/-12.9% versus anti-M2: 24.6+/-10.8%, p=0.047 and control: 7.9+/-3.0% versus anti-M2: 3.3+/-1.3%, p=0.012; respectively). Cell proliferation in the neointimal layer of the vessel five days post-injury was reduced with the blocking of the Mac-1-GPIba interaction (control: 5.0+/-2.9% of the cell total versus anti-M2: 1.8+/-0.5%; p=0.043), along with a significant decrease in cell proliferation in the vessel neointimal layer 28 days post-injury (control: 3.8+/-1.7% versus anti-M2: 2.0+/-1.2%; p=0.047). The blocking of the Mac-1-GPIba interaction also determined a statistically significant decrease of the intimal thickening 28 days post-injury (control: 10,395+/-3,549 microm(2) versus anti-M2: 4,561+/-4,915 microm(2); p=0.012). Leukocyte recruitment after a vascular injury depends on the Mac-1-GPIba interaction and the neutralization of this interaction inhibits cell proliferation and neointimal formation.

Autoantibodies against M1 muscarinic acetylcholine receptor in myasthenic disorders

The Lambert-Eaton myasthenic syndrome (LEMS), often associated with small-cell lung carcinoma (SCLC), is a disorder of acetylcholine (ACh) release from motor nerve terminals. In most patients, it is caused by autoantibodies against the P/Q-type voltage-gated calcium channels (VGCC) that trigger ACh release. However, these antibodies are not detected in approximately 15% of clinically and electrophysiologically typical cases. The M1-type pre-synaptic muscarinic ACh receptor (M1 mAChR) modulates cholinergic neuromuscular transmission by linking to P/Q-type VGCC, and may partially compensate for the reduced calcium entry. Immunoblotting against solubilized human M1 mAChR, we detected autoantibodies in: (a) 14 of 20 (70%) anti-VGCC-positive LEMS patients; (b) all five anti-VGCC-negative LEMS patients, one of whose serum had previously passively transferred LEMS-type electrophysiological defects to mice; (c) all five LEMS patients with autonomic symptoms; (d) seven of 25 (28%) myasthenia gravis (MG) patients in whom increased ACh release partially compensates for post-synaptic defects; (e) none of 10 SCLC patients without LEMS. Although not proving primary pathogenicity of anti-M1 mAChR antibodies, the present results highlight their potential to affect synaptic compensatory mechanisms, more in LEMS than MG.

Amyloid‐beta reduction by memapsin 2 (beta‐secretase) immunization

Memapsin 2 (beta-secretase, BACE1) is the protease that initiates cleavage of beta-amyloid precursor protein leading to the production of amyloid-beta (Abeta) and the onset of Alzheimer's disease (AD). Reducing Abeta by targeting memapsin 2 is a major strategy in developing new AD therapy. Here, in a proof-of-concept study, we show that immunization of transgenic AD mice (Tg2576) with memapsin 2 resulted in Abeta reduction and cognitive improvement. To study the basis of this therapy, we demonstrated that anti-memapsin 2 (anti-M2) antibodies were rapidly internalized and reduced Abeta production in cultured cells. These antibodies also effectively crossed the blood-brain barrier to reach the brain. Two- and 10-month Tg2576 mice were immunized and monitored over 10 and 6 months, respectively. We observed a significant decrease of plasma and brain Abeta40 and Abeta42 (approximately 35%) in the immunized mice as compared to controls. Immunized mice also showed better cognitive performance than controls in both cohorts. Brain histological analyses found no evidence of T cell/microglia/astrocyte activation in the immunized mice, suggesting the absence of inflammatory responses. These results suggest that memapsin 2 immunization in Tg2576 was effective in reducing Abeta production and improving cognitive function and that the current approach warrants further investigation as a therapy for AD.

Inappropriate sinus tachycardia may be related to an immunologic disorder involving cardiac β andrenergic receptors

The mechanisms underlying inappropriate sinus tachycardia are not fully known. An autonomic imbalance seems to play a role, but no attempts have been made to investigate a relationship between this arrhythmia and the antiautonomic membrane receptor antibodies found in other heart disorders and arrhythmias. The purpose of this study was to investigate the prevalence and the functional and biochemical effects of circulating antiautonomic receptor antibodies in patients with inappropriate sinus tachycardia. We studied 21 patients with inappropriate sinus tachycardia and 15 healthy volunteers. The chronotropic effects of the IgG fractions (also of affinity-purified anti-beta1 adrenergic receptor antibodies in selected cases) were assessed on cultured cardiomyocytes before and after exposure to atropine and propranolol. The effects of the IgG fractions from five patients and five healthy volunteers on cAMP production were evaluated in COS-7 cells transfected with genes encoding for beta1 or beta2 adrenergic receptor. The IgG fractions from patients with inappropriate sinus tachycardia exerted a positive chronotropic action with a high prevalence of anti-beta receptor antibodies (52%) and induced a clear-cut and long lasting increment of cAMP. No anti-M2 cholinergic receptor antibodies were found. The IgG fractions from healthy volunteers did not contain antiautonomic receptor antibodies. Our results suggest, for the first time, a link between inappropriate sinus tachycardia and circulating anti-beta adrenergic receptor antibodies that induce a persistent increment in cAMP production. This finding offers new insight into the physiopathology of inappropriate sinus tachycardia with potential therapeutic consequences.

Epidermal Growth Factor Induces Tyrosine Phosphorylation, Membrane Insertion, and Activation of Transient Receptor Potential Channel 4

Various members of the canonical family of transient receptor potential channels (TRPCs) exhibit increased cation influx following receptor stimulation or Ca(2+) store depletion. Tyrosine phosphorylation of TRP family members also results in increased channel activity; however, the link between the two events is unclear. We report that two tyrosine residues in the C terminus of human TRPC4 (hTRPC4), Tyr-959 and Tyr-972, are phosphorylated following epidermal growth factor (EGF) receptor stimulation of COS-7 cells. This phosphorylation was mediated by Src family tyrosine kinases (STKs), with Fyn appearing to be the dominant kinase. In addition, EGF receptor stimulation induced the exocytotic insertion of hTRPC4 into the plasma membrane dependent on the activity of STKs and was accompanied by a phosphorylation-dependent increase in the association of hTRPC4 with Na(+)/H(+) exchanger regulatory factor. Furthermore, this translocation and association was defective upon mutation of Tyr-959 and Tyr-972 to phenylalanine. Significantly, inhibition of STKs was concomitant with a reduction in Ca(2+) influx in both native COS-7 cells and hTRPC4-expressing HEK293 cells, with cells expressing the Y959F/Y972F mutant exhibiting a reduced EGF response. These findings represent the first demonstration of a mechanism for phosphorylation to modulate TRPC channel function.

Detection of autoimmune parameter of SARS patients

To explore whether autoimmune phenomena exist in SARS patients, and to seek for unusual autoimmune antibodies in SARS patients. Autoantibodies against cell nuclei (ANA), autoantibodies against smooth muscles (SMA), autoantibodies against parietal cells (PCA), autoantibodies against heart cells (HRA) were detected by using immunofluorescence, and autoantibodies against live-kidney microsomes (LKM) and anti-M2 antibodies were detected by ELISA in sera taken from 27 SARS patients and 18 healthy controls. Immunofluorescence was used to localize the targets antigens in slides with biochips of lung (monkey) of SARS associated antibodies. ANA, AMA, LKM and SMA were found positive in 3, 1, 1, and 1 of the 27 SARS sera. In 18 healthy control sera, one ANA and one AMA were positive. Statistical analysis showed that there were no difference between two groups in every item detected. Twenty-six of 27 SARS patients and 5 of 18 healthy controls had strongly stained columnar epithelia of the bronchiole, especially the lumen border of the epithelia?the difference between two groups was significant. No antibodies against organs but lung were found in SARS patients. There are auto antibodies against lung tissues in sera of SARS patients.

DNA Topoisomerase II Poison TAS-103 Transactivates GC-Box-dependent Transcription via Acetylation of Sp1

Drug-induced modifications of transcription factors play important roles in both apoptosis and survival signaling. The data presented here show that the DNA topoisomerase II poison TAS-103 transactivated the SV40 promoter in a GC-box-dependent manner and induced Sp1 acetylation in cells expressing p300. This activity was not observed in cells lacking p300. TAS-103 treatment also enhanced the p300 content of the nucleus and the interaction of p300 with Sp1. Cellular susceptibility to TAS-103 was correlated with p300 expression but not with topoisomerase II expression. Furthermore, the presence of p300 significantly sensitized cancer cells to TAS-103 but not to cisplatin. Taken together, these findings demonstrate novel genomic responses to anticancer agents that modulate Sp1 acetylation and Sp1-dependent transcription in an apoptotic pathway.

The toll-like receptor repertoire of human B lymphocytes: inducible and selective expression of TLR9 and TLR10 in normal and transformed cells

AbstractThe present study was designed to investigate the expression of members of the toll-like receptor (TLR) family in human B cells. High-density, resting, and low-density activated tonsillar B cells expressed TLR9 and TLR10 mRNA transcripts at the highest levels. Expression was higher in activated B cells than in resting cells. Analysis of a range of resting and activated human leukocyte populations revealed that mRNA expression of TLR10 was restricted to B cells. Stimulation of resting B cells with anti-μ and anti-CD40 antibodies or with Staphylococcus aureus Cowan I bacteria (SAC) increased expression of TLR9 and TLR10. TLR1 and TLR4 expression were not significantly induced by B-cell activation. Interestingly, a CpG oligonucleotide, a TLR9 agonist, also stimulated TLR9 expression in B cells. Exposure to anti-μ antibodies augmented TLR9 expression, concomitantly and dramatically increasing the responsiveness of B cells to CpG oligonucleotides in terms of proliferation and chemokine (CC chemokine ligand 3 [CCL3] and CCL22) production. Epstein-Barr virus (EBV)–transformed cell lines and other cell lines representative of mature B-cell neoplasias (Burkitt lymphoma, follicular lymphoma, multiple myeloma) expressed TLR9 and/or TLR10, whereas pre-B cell lines were negative. These results show that normal and neoplastic human B lymphocytes express a distinct TLR repertoire including TLR9 and TLR10 and that expression is increased upon engagement of the antigen receptor complex or TLR9 itself. Regulated expression of selected TLRs in B cells is likely to play an important role in linking innate and adaptive immune responses in normal and pathologic conditions.

EGTA treatment of human airways in vitro unmasks M1/MUC5AC mucin in submucosal glands.

Mucin staining can be used to evaluate secretory activity of human airways. However, mucin epitopes may be masked by physicochemical properties of the secretions. The aim of this investigation was to examine the effects of the calcium chelator, ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) on the detection of M1/MUC5AC mucin in isolated human bronchial preparations. Immunohistochemical investigation and immunoradiometric assays with anti-M1 monoclonal antibodies (Mabs) were used to detect M1/MUC5AC mucin derived from bronchial preparations with an intact surface epithelium, or in tissues where the epithelium had been removed (rubbed preparations). The Mabs labelled both epithelial goblet cells and submucosal glandular cells in EGTA (4 mM)-exposed bronchial preparations, while only goblet cells were stained in EGTA (0.4 mM)-exposed tissues. The quantities of M1/MUC5AC mucin detected in either the bronchial fluids derived from EGTA (4 mM)-exposed intact and rubbed preparations or in bronchial fluids treated with EGTA (4 mM) were significantly increased by two-fold when compared with untreated control values (p<0.001). In addition, lactate dehydrogenase (LDH) activity and protein measurements were unaltered during exposure of human airways to EGTA (4 mM) suggesting that this treatment did not affect tissue viability. These results provide evidence that ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraacetic acid (4 mM) facilitates the detection of M1/MUC5AC mucin by altering the physicochemical properties of respiratory mucin, thereby exposing epitopes with which anti-M1 monoclonal antibodies are reactive. This will allow more accurate measurement of secretory activity in human airways in vitro.

False positive reaction in ELISA for IgM class anti-M2 antibody and its prevention

Anti-M2 of anti-mitochondrial antibodies is recognized as the specific autoantibody detected in sera from patients with primary biliary cirrhosis (PBC). The IgG class and IgM class of this antibody can be separately measured using each ELISA. In the present study, false positive reactions were found in some sera from non-PBC patients such as acute hepatitis A, syphilis and rheumatoid arthritis using the IgM anti-M2 ELISA. They showed an increase of polyclonal IgM, and positivity for IgM anti-cardiolipin or rheumatoid factors, respectively. So, we developed a means to prevent these false positive reactions. First, dilutions of test sera at 1:1000-fold were carried out in addition to the original method at 1:100-fold. Secondly, some blocking reagents were added into the buffer system. By serum dilution, non-specific bindings disappeared in most samples other than showing an increase in polyclonal IgM. Moreover, the addition of suitable blocking reagents such as fetal bovine serum (FBS) and skimmed milk into the buffer system could prevent these non-specific bindings. From these findings, the procedure of optical serum dilution and the addition of suitable blocking reagents successfully prevented false positive reactions in this IgM anti-M2 ELISA.

In vitro production of immunoglobulins of various classes and subclasses by cord blood B cells in African neonates: modeling and assessment of determination

Cord blood B cells obtained from neonates of healthy Senegalese mothers were assayed in vitro for their capacity to fully differentiate and secrete immunoglobulins (Ig) of various classes and subclasses. Stimulation of mononuclear cells with SAC particles or anti-μ antibodies in the presence of IL-4, or with IL-2 and IL-10 induced a strong production of IgG, provided that an additional CD40/CD40L signal was present, in contrast to adult cell cultures. Cord blood mononuclear cells differentially stimulated with various cytokines in order to lead to Ig heavy chain switching and production of the various classes/subclasses consistently produced IgG1, IgG3, IgG4, IgE and IgA. This system has been applied to immune cells from African neonates that have not been extensively studied previously. Estimation of Ig production as OD ratios could be applied to cultures where cord blood B cells are stimulated with defined antigens of human pathogens to which the fetus immune system was primed in utero.

Localization of recombination activating gene 1/green fluorescent protein (RAG1/GFP) expression in secondary lymphoid organs after immunization with T-dependent antigens in rag1/gfpknockin mice

AbstractSecondary rearrangements of immunoglobulin gene segments that generate a new antibody repertoire in peripheral B cells have been described as receptor revision and occur by as yet unknown mechanisms. To determine the importance of recombination activating gene (RAG) expression in receptor revision, heterozygous rag1/green fluorescent protein (gfp) knockin mice were used to examine the location of RAG1 expression in the germinal centers (GCs) of lymphoid follicles after immunization with a variety of T-cell–dependent antigens. Immunization of rag1/gfp heterozygous mice orrag1 homozygous knockout mice reconstituted withrag1/gfp heterozygous spleen cells caused the down-regulation of RAG1/GFP signal in GCs. Although some RAG1/GFP+ cells appeared in regions surrounding the peanut agglutinin (PNA)+GL-7+ GC area, RAG1/GFP+ cells did not accumulate in the central region. In addition, the stimulation of spleen B cells with anti-μ antibody plus interleukin-4 (IL-4) or with anti-CD40 monoclonal antibody plus IL-7 did not induce GFP signals at detectable levels in vitro. These results clearly demonstrate that RAG1 re-expression either does not occur or is at extremely low levels in antigen-driven B cells in GCs of secondary lymphoid follicles, suggesting that other mechanisms may mediate the gene rearrangements observed in receptor revision.

B-Cell Suppression in Adult Mice Injected with Anti-δ Followed by Anti-μ mAb

Cross-linking of surface IgM or IgD B-cell receptors (BCR) with appropriate anti-Ig antibodies induces IgMhigh or IgDhigh B-cell depletion, respectively. The aim of this paper is to analyze how injections of anti-δ followed by anti-μ monoclonal antibodies (mAb) can deplete and suppress B cells and then induce T-independent type 2 antigen tolerance in adult mice even after treatment is stopped. The experimental protocol consisted of three daily injections of anti-δ mAb followed by repeated injections of anti-μ mAb. It shows that a sequential injection of anti-δ and anti-μ mAb induces B-cell depletion and T-independent type 2 response downregulation. Morever, the T-dependent response is maintained, except for the IgG3 isotype. After clearance of the anti-δ mAb from the circulation, B cells reappear as an IgD+ IgM− B-cell population in the bone marrow (BM) and spleen. The origin of IgD+ IgM− cells was studied in scid mouse transfer models. We show that IgD+ IgM− B cells are not mature cells reexpressing sIgD but BM-derived cells that require a T-cell presence to be developed. The lack of sIgM expression by posttranscriptional regulation and the need of T-cell help for escaping anti-μ negative selection suggest strongly that this population had properties similar to those of anergized B cells. These results support the potential use of sequential injections of anti-δ and anti-μ in the prevention of xenograft rejection.

Protection against Measles Virus-Induced Encephalitis by Anti-mimotope Antibodies: The Role of Antibody Affinity

Synthetic peptides mimicking a conformational B-cell epitope (M2) of the measles virus fusion protein (MVF) were used for the immunization of BALB/c mice and the anti-peptide and anti-virus antibody titers induced were compared. Of the panel of tested peptides, a chimeric peptide consisting of two copies of a T-helper epitope (residues 288–302 of MVF) and one copy of the mimotope M2 (TTM2) and a multiple antigen peptide with eight copies of M2 (MAP-M2) induced the highest titers of anti-M2 and anti-MV antibodies. Furthermore, peptides TTM2 and MAP-M2 induced antibodies with highest affinity for the mimotope and highest avidity for measles virus. Immunization with the MAP-M2 construct induced high titers of high-affinity anti-M2 antibody despite the absence of a T-helper epitope, and lymphocyte proliferation data suggest that the addition of M2 to the MAP resulted in the generation of a structure capable of stimulating T-cell help. Sera with anti-M2 reactivity were pooled according to affinity values for binding to M2, and high- and low-affinity pools were tested for their ability to prevent MV-induced encephalitis in a mouse model. The high-affinity serum pool conferred protection in 100% of mice, whereas the lower affinity pool conferred protection to only 50% of animals. These results indicate the potential of mimotopes for use as synthetic peptide immunogens and highlight the importance of designing vaccines to induce antibodies of high affinity.

Immature B lymphocytes from adult bone marrow exhibit a selective defect in induced hyperexpression of major histocompatibility complex class II and fail to show B7.2 induction.

Mature B lymphocytes respond to antigen receptor ligation by phenotypic changes, including up-regulation of major histocompatibility complex class II molecules and expression of B7.2, which are required for initiating and sustaining a productive interaction with T helper cells. We have previously demonstrated that neonatal B cells fail to show a similar up-regulation of class II and B7.2 expression following B-cell receptor (BCR) ligation, although these responses could be induced by other stimuli. Here we demonstrate that immature B cells from adult bone marrow exhibit even more profound defects in these responses, as they fail to up-regulate class II in response to either BCR ligation or interleukin-4. Moreover, bone marrow-derived, immature B cells could not be induced to express B7.2 either by receptor cross-linking or by lipopolysaccharide. These differences in the inducible expression of class II and B7.2 appear to be intrinsic to the B cells, as they were retained in purified populations of B-lineage cells and could not be induced in mature B cells by co-culture with bone marrow cells. Furthermore, short-term culture of bone marrow permitted B-cell maturation, which was accompanied by acquisition of responsiveness to the same stimuli as mature, splenic B cells. The inability of immature B cells to show these responses provides a molecular explanation for their reported deficiency in interacting with T cells. Failure of immature B cells to inducibly express B7.2 may also be important for the establishment of self tolerance in the B-cell compartment.

Autoantibodies against the beta- and muscarinic receptors in cardiomyopathy.

The sera of patients with idiopathic dilated cardiomyopathy and the Chagas' disease contain agonist-like autoantibodies directed against the beta 1-adrenoceptor and/or the muscarinic M2-receptor. The anti-beta 1-adrenoceptor antibodies could be directed against amino acid sequences of the first or second extracellular loop. In patients with dilated cardiomyopathy the first as well as the second extracellular loop was identified as an antibody epitope. In Chagas' disease the anti-beta 1-adrenoceptor antibody recognizes only 1 epitope on the second extracellular loop. The anti-beta 1-adrenoceptor antibodies acting like the beta-adrenergic agonist isoprenaline and exert a positive chronotropic effect in cultured rat cardiomyocytes. In contrast to isoprenaline the antibody caused no downregulation of the beta-adrenergic signal transduction cascade within 6 hours. The anti-M2 receptor antibodies recognize in both diseases an epitope on the second extracellular loop. The anti-M2-receptor antibody exert a negative chronotropic response in cultured cardiomyocytes. This antibody induced no downregulation of the muscarinic M2-receptor. The negative chronotropic effect was unabated for 6 hours. Based on these findings it is believed that the agonist-like autoantibodies that act against the beta 1-adrenoceptor and the muscarinic M2-receptor may play a role in the pathogenesis of dilated cardiomyopathy and Chagas' disease.

Analysis of two major anti-M2 antibodies (anti-PDC-E2/anti-BCOADC-E2) in primary biliary cirrhosis: relationship to titers of immunofluorescent anti-mitochondrial antibody

To analyze anti-M2 components in primary biliary cirrhosis (PBC) we measured two major anti-M2 antibodies (anti-PDC-E2 and anti-BCOADC-E2) by immunoblotting and ELISA, and compared the results between 38 immunofluorescent anti-mitochondrial antibody (AMA)-negative PBC patients (group A) and 39 strongly AMA-positive PBC patients (group B) with titers of 1:640. Using bovine heart mitochondrial fraction as antigen, the immunoblot positivity rate of anti-PDC-E2 in group B was significantly higher than that in group A, whereas the positivity rate of anti-BCOADC-E2 was not significantly different between the two groups. This result was similar to that obtained by ELISA using recombinant fusion proteins. In group A there was a significant inverse correlation between ELISA optical density values of anti-PDC-E2 and of anti-BCOADC-E2, but in group B there was no correlation between the two values. Only three patients from group A and 21 from group B were positive for both antibodies. Taken together these results appear to indicate that the detection of anti-BCOADC-E2 is critical for the accurate serological diagnosis of AMA-negative PBC patients. The detection of anti-BCOADC-E2 may also help to distinguish between AMA-negative PBC and autoimmune cholangitis patients.

My4+/LeuM3- Molecule and CD19 Antigen Are Down-Modulate by Low Affinity Fc Gamma Receptor II (CD32) Stimulation on CD56-Positive B - Lymphoma Cells

My4+/LeuM3- molecule is recognized by My4, but not by LeuM3, both well known mAbs to CD14. In a previous study we showed that the My4+/LeuM3- molecule on a human mono-blastic cell line, U937, is not CD14, but another cell surface antigen. The roles and functions of the My4+/LeuM3- molecule remained unknown. We now report that specific stimulation of FcyR with aggregated IgG or anti-FcγRII antibody down-modulated the My4+/LeuM3- molecules, as well as CD 19, in a case of CD56-positive B cell lymphoma. Stimulation of FcγR with anti-μ antibody, which induced concomitant stimulation of slg, did not induce down-modulation of either molecule. Stimulation of CR2 (CD21), a protein which is functionally or physically associated with CD 19, with anti-CR2 (CD21) mAbs also had no effect. The modulation occurred specifically on CD56-positive B-lymphoma cells, since My4+/LeuM3- -positive, CD56-negative B-lymphoma cells did not respond to the stimulation. These results suggest that CD 19 and My4+/LeuM3- molecules are functionally or physically associated with FcyR II on CD56 positive B-lymphoma cells defined as being at a terminal B cell differentiation stage.

ATP induced MUC5AC release from human airways in vitro.

Chronic airway diseases are often associated with marked mucus production, however, little is known about the regulation of secretory activity by locally released endogenous mediators. This investigation was performed to determine the release of MUC5AC mucin from human bronchial preparations using the purinergic agonists adenosine 5'-triphosphate (ATP) and uridine 5'-triphosphate (UTP). Immunohistochemical and immunoradiometric assays (IRMA) were used to detect the MUC5AC mucin. Immunohistochemical analysis were performed using individual 1-13 M1 and 21 M1 MAbs recognizing a recombinant M1 mucin partially encoded by the MUC5AC gene. IRMA measurments were performed using a mixture of eight anti-M1 mucin MAbs (PM8), which included both 1-13 M1 and 21 M1 MAbs. Lysozyme and protein were also measured in the biological fluids derived from human bronchial preparations obtained from patients who had undergone surgery for lung carcinoma. The anti-M1 monoclonal antibodies labelled epithelial goblet cells. After challenge of human bronchial preparations with ATP, the goblet cells exhibited less staining. In contrast, UTP did not alter the immunolabelling of goblet cells. MUC5AC mucin in the bronchial fluids derived from ATP-challenged preparations was increased while UTP had no effect on release. ATP did not alter either the quantities of lysozyme or protein detected in the biological fluids. These results suggest that ATP may regulate epithelial goblet cell secretion of MUC5AC mucin from human airways in vitro.