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PubMed1989

[Changes in complement breakdown products and terminal complement complex in patients with acute glomerulonephritis].

In this study we examined the role of the complement system in acute glomerulonephritis (AGN). Breakdown products of complements (iC3b, C4d and Bb) and Terminal complement complex (TCC, SC5b-9 complex) in plasma samples were measured by ELISA. The microassay plates were coated with monoclonal antibodies which bind specifically to human iC3b, C4d, Bb and SC5b-9 complex. This assay accurately quantitates small amounts of in vivo complement activation. The plasma samples were drawn from patients with AGN and other glomerulonephritis. There were some patients with various glomerulonephritis whose plasma iC3b, C4d and Bb concentrations were higher than those in normal human. However specificity was not found. The ratios iC3b/C3 and C4d/C4 were increased in the early stages of AGN, but plasma Bb concentrations revealed no significant changes. Plasma SC5b-9 complex concentrations were increased in the early stages of AGN. C3c, C3d, C4d and SC5b-9 were found to be localised in the glomeruli of those AGN patients. It is suggestive that in these cases of AGN (especially case 2) complement activation is predominantly mediated through the classical pathway and TCC is formed by this activation. This complement activation in the blood and the renal tissue is presumed to be involved in the initiation and progression of AGN.

Acute Disease↗
PubMed1995

Complement receptor expression and activation of the complement cascade on B lymphocytes from patients with systemic lupus erythematosus (SLE).

It has previously been reported that the expression of the complement receptors, CR1 on erythrocytes and blood leucocytes and CR2 on B cells, is reduced in patients with SLE, and that the reduced expression of CR1 on erythrocytes is related to disease activity. We have earlier demonstrated that normal B cells are capable of activating the alternative pathway (AP) of complement in a CR2-dependent fashion. In this study we have investigated whether disturbances in this activity may be related to the altered phenotype of SLE B cells. Flow cytometry was used to measure expression of complement receptors and regulatory proteins on B cells from SLE patients, as well as the deposition of C3 fragments occurring in vivo or after in vitro AP activation. We have confirmed, for a proportion of the patients studied, reduced expression of CR1 and CR2 on B cells, and shown a consistency between low CR2 expression and reduced in vitro AP activation in the presence of homologous, normal serum. In addition, the B cells, like erythrocytes, bear raised levels of in vivo-deposited C3dg, but not C3b fragments, compared with normal B cells. The erythrocytes from SLE patients were unable to inhibit in vitro AP activation by B cells in homologous serum. Finally, we demonstrated an inverse relationship between SLE disease activity index (SLEDAI) and the expression of complement receptor 2 (CR2) on SLE B cells. Thus, determination of CR2 on B cells may emerge as an additional laboratory tool in the assessment of SLE activity.

Adult↗
PubMed1986

Complement mediated inhibition of immune precipitation and solubilization generate different concentrations of complement anaphylatoxins (C4a, C3a, C5a).

Complement prevents the formation of insoluble immune complexes (inhibition of immune precipitation (IIP], and solubilizes preformed immune aggregates (solubilization (SOL]. Since the mechanism of complement activation differs in these two reactions, it is possible that they differ also in the amount of complement fragments released, in particular the anaphylatoxins C3a, C5a and C4a. We measured C4 and C3 consumption, and the formation of complement anaphylatoxins during IIP and SOL using two different immune complex models (BSA, rabbit anti-BSA; tetanus toxoid (TT), human anti-TT). At equal immune complex concentrations in both models, SOL was more efficient than IIP at cleaving C3, and more C3a and C5a was released. Comparing the two reactions, C3a formation was followed by more C5 cleavage (C5a) during SOL. Similarly C4a formation (classical pathway activation) was followed by more C3 cleavage (C3a: classical and alternative pathway activations), during SOL. It is suggested that in vivo SOL of insoluble complexes is rapidly accompanied by a damaging phlogistic reaction, whereas IIP produces less inflammation.

Antigen-Antibody Complex↗
PubMed1986

Glycosaminoglycans enhance complement hemolytic efficiency: theoretical considerations for GAG-complement-saliva interactions.

When human serum is diluted and pre-incubated at 37 degrees C in low ionic strength buffer (LIS, u = 0.07; made iso-osmotic with dextrose), a spontaneous activation of complement (C) is observed as determined by C4 and C3 electrophoretic conversion. In this paper it is postulated that most species of glycosaminoglycans (GAG) restricted non-specific fluid phase complement consumption induced by LIS, an effect which conserved complement and thereby enhanced the subsequent residual serum C mediated hemolytic activity. The capacity of glycosaminoglycans, to have modulated the hemolytic activity at low ionic strength, depended on the charge of the GAG species tested. In general, the GAG regulatory effects may have been due to GAG mediated restriction of spontaneous non-specific fluid phase C1 autoactivation, and/or restriction of activated C1 activity. Such effects would result in the subsequent reduction of the spontaneous fluid phase C4 and C3 consumption. Although the precise mechanisms responsible for the effects were not identified, it is speculated that the potentiation of C1 inhibitor function and direct effects on C1 might be involved. Overall, the relative specific activities of the glycosaminoglycans, on a weight basis, in mediating the fluid phase C regulatory effect were heparin greater than dermatan sulfate greater than chondroitin-6-sulfate greater than chondroitin-4-sulfate greater than hyaluronic acid and keratan sulfate. When much higher concns of heparin (greater than or equal 0.2 micrograms/ml) were used, complement mediated lysis of EA was inhibited, probably due to the direct inhibition of C1, even C1 which may have bound to the sensitized erythrocytes (EA). Results similar to that of heparin were obtained using greater than 1 mg/ml of dermatan sulfate or dextran sulfate. In contrast, pre-incubation of human serum in LIS with high concns (up to 10 mg/ml) of hyaluronic acid or chondroitin-4-sulfate, which are much less charged, continued to result only in the restriction of hemolytically non-specific (fluid phase) C consumption, resulting in a higher residual complement hemolytic activity. A theory is developed that the binding of polyionic GAG to C1 and to C1 INH may provide a charged local environment which simulates a relatively higher ionic strength. Chemical degradation of hyaluronic acid or chondroitin-4 or -6 sulfate resulted in lowering of this C modulating effect, indicative of the importance of the structural integrity of these charged glycosaminoglycans.(ABSTRACT TRUNCATED AT 400 WORDS)

Complement Activation↗
PubMedDate not supplied

The significance of red cell bound complement components in development of standards and quality assurance for the anti-complement components of antiglobulin sera.

Human red blood cells, sensitized with complement in vivo and by a variety of methods in vitro, (e.g. blood group antibody, low ionic strength, alternate pathway), were tested with a battery of anti-complement sera (anti-C3, -C3c, -C3d, -C4, -C4c). Red blood cells could be prepared by relatively simple methods to yield cells sensitized with C3 and C4, C3 but not C4, C4 but no C3, C3d with no C3c and C4d with no C4c. These cells are suitable for standarization and quality assurance of antiglobulin sera (AGS). Anti-C3d is necessary for optimal detection of sensitization of red blood cells by complement in vivo by the direct anti-globulin test (DAT). Anti-C3d may also be optimal for the indirect antiglobulin test (IAT) especially if incubation periods greater than one hour are employed. Potent anti-C4 and anti-C3 antisera made in the authors' laboratory resulted in numerous weakly positive antiglobulin tests when testing red blood cells from refrigerated clots (especially anti-C4) but red blood cells from refrigerated anticoagulated segments gave negative results. When red blood cells were incubated in normal serum at room temperature (as in the room temperature phase of a compatibility test), some positive results were again obtained with the potent anti-C4 and anti-C3 antisera. However, one commercial antiglobulin serum containing anti-complement antibodies that were at least as potent as any other commercial antiglobulin serum gave uniformly negative results under the above conditions. Anti-C4 antibodies may be omitted from anti-globulin sera without decreasing the efficacy of such antisera to be used in compatibility testing. Thus, positive results in the compatibility test due to detection of clinically insignificant cold antibodies in the IAT by the anti-complement antibodies in AGS, may be avoided if anti-C4 is omitted or is in low concentration and if the concentration of anti-C3d is carefully standardized. A higher concentration of anti-C3d could be used for compatibility tests if red blood cells from anticoagulated segments were used instead of those from clots and if a separate tube were used for the IAT at 37 C rather than using one tube for both room temperature and 37 C incubations.

Antibody Specificity↗
PubMed1992

Inhibition of the classical activation pathway of complement-mediated lysis by monoclonal antibodies to complement components C3c and C3d.

Eight epitope-mapped monoclonal antibodies (MoAbs) to complement component C3d and five to complement component C3c were investigated to determine whether they could inhibit the classical activation pathway of complement-mediated lysis (CML) by using blood group AB red cells sensitized by A or B MoAbs. Three IgM C3d MoAbs and one IgG1 C3c MoAb were able to inhibit CML in a dose-dependent manner. In the presence of excess complement, no inhibition was observed. The greatest inhibition was observed with two high-affinity IgM antibodies that were specific for epitope 1 on the C3d component. Some inhibition was observed with a high-affinity IgM antibody specific for epitope 3 of the C3d component and also with a lower-affinity IgG antibody specific for epitope 1 of the C3c component. The results indicate that some complement MoAbs have the capacity to distinguish between conformationally and/or functionally different forms of red cell-bound C3.

Antibodies, Monoclonal↗
PubMed1984

Studies on the binding of complement factor C4 in human platelets. Complement activation by means of cold agglutinins.

Normal human platelets were investigated by immunofluorescence techniques for the natural occurrence of and uptake capacity for complement factor C4. Fractions of human platelets were found to carry none or very little C4. Activated C4 was readily taken up by the majority of platelets in vitro. Complement could be activated with pathological cold agglutinins (CA) of mono- or polyclonal types, all with specificity for the I antigen. Complement activation seen in normal human sera was probably due to naturally occurring CA with anti-I specificity. Thrombin potentiated the complement-activating capacity of CA, and complement factor C1 enhanced and stabilized the binding of CA to platelets.

Agglutinins↗
PubMed1989

Local complement activation, thromboxane-mediated vasoconstriction, and vascular leakage in isolated lungs. Role of the terminal complement sequence.

In situ complement activation was induced in isolated, ventilated, and blood-free perfused rabbit lungs. Six to 11% human serum (vol/vol) was repeatedly admixed to the recirculating Krebs Henseleit buffer during 10-min periods, interrupted by rinsing phases with serum-free medium. This caused dose-dependent, reversible, and reproducible pulmonary artery pressor responses with pressure peaks or plateaus of 8 to 22 mm Hg. Pressor responses were paralleled by a marked release of thromboxane (TxA2) and prostaglandin I2 into the medium. Heat-inactivated serum, purified fluid-phase SC5b-9, and serum that had been activated with inulin in the absence or presence of a carboxypeptidase inhibitor all failed to elicit pressor responses. Both pressor response and prostanoid release were strictly dependent on complement factor C8, and evidence for C8 binding was obtained with the use of 125I-C8. Inhibitor studies collectively indicated that TxA2 was the predominant vasoconstrictive agent. Although repetitive short-term application of human serum induced no major lung weight gain, prolonged exposure to serum (40 to 80 min) without intermittent rinsing phases caused a delayed increase in the capillary filtration coefficient to maximally 3- to 4-fold values, with marked lung edema formation. We conclude that in situ activation of complement in the rabbit lung vasculature causes immediate intrapulmonary prostanoid generation and thromboxane-mediated vasoconstriction, independent of circulating leukocytes, but dependent on the formation of terminal membrane-complement complexes. Continuous complement activation results in a delayed increase in lung vascular permeability.

Animals↗
PubMed1989

Prelesional complement activation in experimental atherosclerosis. Terminal C5b-9 complement deposition coincides with cholesterol accumulation in the aortic intima of hypercholesterolemic rabbits.

Cholesterol accumulation in the tunica intima of large and medium sized arteries is a characteristic of atherosclerotic lesion development. Cholesterol activates the complement system in vitro generating C5b-9 complexes, and C5b-9 antigens have been observed in atherosclerotic lesions. We therefore investigated whether complement activation correlates temporally with accumulation of intimal cholesterol in vivo. Frozen sections of aortic tissue from rabbits fed a 0.3% cholesterol diet for 0, 2, 6, and 10 weeks were stained with antibodies directed against neoantigens of the C5b-9 complex. Lipids were detected with oil red O, filipin, and antibodies against apoprotein B. C5b-9 complexes were observed to colocalize with extracellular lipid in the subendothelial space beginning at 2 weeks on the diet and extending past 10 weeks. Quantitation of aorta extracted C5b-9 complexes by an enzyme-linked immunosorbent assay revealed a progressive increase in aortic C5b-9 content as a function of time on the cholesterol diet. An approximately 30-fold increase in aortic C5b-9 occurred between 0 and 10 weeks on the diet, whereas plasma C5b-9 remained at normal levels throughout this time. Aortic cholesterol and triglyceride levels approximately doubled between 0 and 10 weeks on the diet and plasma cholesterol increased nearly 50-fold. Intimal C5b-9 deposition preceded monocyte infiltration and foam cell development. The data indicates that early cholesterol accumulation in the aortic intima results in complement activation. Since complement activation products are chemotactic for monocytes and promote their adhesion to the endothelium, complement may provide a mechanism by which monocytes are attracted to arterial regions of lipid accumulation.

Animals↗
PubMed1985

Disease-associated loss of erythrocyte complement receptors (CR1, C3b receptors) in patients with systemic lupus erythematosus and other diseases involving autoantibodies and/or complement activation.

Although surface membrane density of complement receptor type one (CR1) on erythrocytes (E) is probably an inherited trait among normal individuals, recent evidence from our laboratories suggests that the reduced number of CR1 per E observed in patients with systemic lupus erythematosus (SLE) results from acquired as well as genetic factors. In the present investigation, the number of CR1 per E was quantitated with 125I-monoclonal anti-CR1 and was found to vary inversely with disease activity in patients with SLE who were followed serially for as long as 14 mo. Although evidence for E surface-bound immune complexes or fixed C3b/iC3b was not obtained, periods of disease activity and low amounts of CR1 per E correlated with the presence of 100 to 800 molecules per E of fixed C3dg fragments (less than 100 C3dg per E in normal subjects). Reduced CR1 and excess fixed C3dg on E also were observed in patients with other disorders associated with complement activation, including chronic cold agglutinin disease, autoimmune hemolytic anemia, paroxysmal nocturnal hemoglobinuria (PNH), Sjögren's syndrome, and mycoplasma pneumonia. A significant negative correlation (r = -0.498) between CR1/E and fixed C3dg/E was demonstrable in 255 individual assays evaluated by regression analysis. CR1 decreased and fixed C3dg increased during active disease; the converse was obtained during remission. In patients with active SLE, both serum complement activity and E CR1 decreased, whereas fixed C3dg fragments increased. By piecewise linear regression analysis, the appearance of 100 to 400 C3dg molecules on patients' E corresponded to a 27 to 60%, reduction in the number of CR1 per E (p less than 0.0002), confirming that fixation of C3 to E was correlated with a loss of CR1. In patients with PNH, low values for CR1 were observed on moderately complement-sensitive PNH type II E in association with increased fixed C3 fragments; however, the markedly complement-sensitive PNH type III E had essentially normal amounts of CR1 and bore little fixed C3. The addition of soluble DNA/anti-DNA immune complexes to normal blood generated levels of fixed C3dg fragments on E comparable to those observed on E from patients with SLE. Kinetic experiments indicated that C3b was fixed to E during the process of immune complex binding and release from E CR1, and that this fixed C3b was subsequently degraded rapidly to fixed iC3b and more slowly to fixed C3dg without the loss of CR1 that occurs in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Anemia, Hemolytic↗
PubMed1986

Complement activation in rheumatoid arthritis evaluated by C3dg and the terminal complement complex.

Complement activation was evaluated in plasma and synovial fluid from patients with rheumatoid arthritis. The activation fragment C3dg and the fluid-phase terminal complement complex were used as indicators of initial and terminal activation, respectively. Considerable activation of the whole complement cascade was demonstrated in most synovial fluid samples and in one-third of the plasma samples. No correlation was found between the level of activation products in synovial fluid and the level in plasma. Therefore, both compartments must be examined in order to evaluate local and systemic complement activation in rheumatoid arthritis.

Arthritis, Rheumatoid↗
PubMed1992

Assessment of complement activation in clinical samples. Comparison of immunochemical and functional measurements of complement components with quantitation of activation fragments.

We have compared functional and immunochemical measurements of complement components with assays measuring the generation of activation fragments, for the assessment of classical pathway activation in vitro and in vivo. The generation of the C3a, C3b/C3bi cleavage fragments of C3, and of the C4d cleavage fragment of C4 measured by ELISA and RIA, was correlated with the decrease in total complement hemolytic activity (CH50) and in functional activity of C3 and C4 in normal human serum in which the classical pathway had been activated with aggregated IgG. The decrease in CH50 in in vitro activated serum was also correlated with the generation of C5a and soluble SC5b-9 complexes. In contrast, no or little increase in the concentration of C3a, C3b/C3bi and C4d was observed in plasma samples from patients with low CH50 and with low levels of immunochemical C3 and C4, indicating that fragment quantitation assays provide no information on the presence and extent of complement activation in vivo. Analysis of samples from patients expressing the four C4 genes and patients having one or two C4 null alleles indicated that a ratio of hemolytic C4 to C2 > or = 1 was indicative of complement activation without C4 deficiency, whereas a ratio below 1 was indicative of C4 deficiency with or without classical pathway consumption. Classical pathway activation and C4 deficiency in clinical samples are best predicted by the concomitant assessment of immunochemical levels of C3 and C4 and hemolytic levels of C4, C2 and C3.

Complement Activation↗
PubMed1985

Early- and late-phase activation of complement evaluated by plasma levels of C3d,g and the terminal complement complex.

Activation of the initial part (early phase) and terminal part (late phase) of the complement cascade was examined. C3d,g and the fluid-phase terminal complement complex were quantified and compared after spontaneous in vitro activation and after acute in vivo activation caused by extracorporeal circulation during coronary artery surgery. The results suggest that there is a close but not complete correlation between early- and late-phase activation of complement, that C3d,g and the terminal complement complex have different elimination rates in vivo, and that these two indicators are valuable for evaluation of early- and late-phase activation, respectively.

Complement Activation↗
PubMed1987

Immunocytochemical localisation of complement components C8 and C9 in human diseased muscle. The role of complement in muscle fibre damage.

The localisation of the complement components C8 and C9 was studied immunocytochemically in human diseased muscle to determine the role of complement in muscle fibre damage. Monoclonal antibodies to 2 epitopes of C9 and a monoclonal antibody to the alpha subunit of C8 were applied to frozen sections of muscle biopsies from 9 cases of dermatomyositis, 5 cases of polymyositis, 7 cases of Duchenne muscular dystrophy and 4 cases of Becker muscular dystrophy. These were compared with 6 control biopsies which were morphologically normal. In all cases of inflammatory myopathies several non-necrotic fibres showed discrete peripheral patches of C9 and to a lesser extent C8. In the muscular dystrophies peripheral C9 was observed on a few non-necrotic fibres and basophilic fibres showed C9 between the fibres as well as at the periphery. In all cases necrotic fibres labelled intensely with C9 and C8 but intensities varied with the different monoclonal antibodies. This was thought to result from differences in the polymerisation of the C9 molecule in the membrane attack complex. Complement C8 and C9 were also localised to blood vessels in 3 cases of muscular dystrophy, 2 cases of polymyositis and all cases of juvenile dermatomyositis. No complement was observed in the control samples. Our results provide evidence for the sublytic formation of the membrane attack complex (MAC) on non-necrotic fibres in inflammatory myopathies and muscular dystrophy. This sublytic formation of the MAC may induce sublethal metabolic damage, mediated by calcium, and suggests a primary role of complement in muscle damage not only in inflammatory disorders but also muscular dystrophy.

Adolescent↗
PubMed1981

Permeability characteristics of complement-damaged membranes: evaluation of the membrane leak generated by the complement proteins C5b-9.

Permeability characteristics of the membrane lesion generated by the terminal complement proteins are considered in light of recent observations that the measured diffusion of solute across complement-damaged membranes does not conform to the "doughnut hole" model of a discrete transmembrane pore formed by the inserted C5b-9 complex. By using the measured kinetics of steady-state tracer isotope diffusion of nonelectrolytes across resealed erythrocyte ghost membranes treated with C5b-9, a new transport model is developed. This model considers the apparent membrane lesion strictly in terms of the operational criteria of a functional conducting pathway for the observed diffusing solute, independent of a priori assumptions about the geometry or molecular properties of the membrane lesion. With this definition of the unit membrane lesion and the assumption that the exclusion size of the conducting pathway varies directly with the multiplicity of bound C5b-9 (as suggested by previous measurements under conditions of varying input of C5b-9), numerical estimates of te apparent permeability of the complement-damaged membrane to four diffusing nonelectrolytes are derived. These results suggest that the pathway for a particle diffusing across the complement lesion cannot be a pore and is functionally equivalent to an aqueous leak pathway, free of pore constraints. Implications of these results are discussed in terms of current molecular models for the mechanism of membrane damage by the complement proteins.

Biological Transport↗
PubMed1995

Purification and characterization of a human membrane protein that activates the alternative complement pathway and allows the deposition of homologous complement C3.

A human myeloid cell subline, P39+, is found to be a target for human complement (C) via the alternative pathway and to allow the deposition of multiple C3 fragments on its membranes, though expressing the complement regulatory proteins decay-accelerating factor and membrane cofactor protein. The parent cell line, P39-, which is phenotypically similar to the P39+ subline, does not allow the deposition of homologous C3 fragments. In this study, we established a monoclonal antibody, M161 Ab, which reacted with P39+ but not P39- cells. This Ab recognized a 43-kD protein in P39+ cell lysate transblotted onto nitrocellulose. Using this Ab as a probe, we purified the 43-kD protein, namely, M161 antigen (Ag). M161 Ag had a basic isoelectric point (pI), 9.3-9.4 by chromatofocusing, and was precipitated as an insoluble material at the pI point. The purified M161 Ag was a single-chain protein and did not possess N- or O-linked carbohydrates. When the purified M161 Ag was transblotted onto nitrocellulose and incubated with Mg(2+)-EGTA serum, human C3 fragments were efficiently deposited on M161 Ag. The major species of the deposited C3 fragments was C3b. Furthermore, the C3 fragments bound to the M161 Ag were detached by 1 M hydroxylamine, suggesting that a covalent ester linkage sustains M161 Ag-C3b interaction. NH2-terminal amino acid analysis revealed that M161Ag is a novel membrane protein. Hence, it appeared that M161 Ag is a potent activator of human alternative complement pathway on human cells that activates homologous C3 and allows the deposition of C3b on itself. Thus, under some conditions, homeostasis of complement is maintained even on human cells, not only by the complement regulatory proteins, but also by membrane C3-activating molecules on which C3b is deposited.

Antibodies, Monoclonal↗
PubMed1991

Complement activation by house dust: reduced reactivity of serum complement in patients with bronchial asthma.

Among ten different allergens, house-dust extract proved to be the most potent complement activator. It was therefore chosen to investigate the susceptibility of complement in the serum and bronchoalveolar lavage fluid of patients with extrinsic asthma and control persons. Complement activation in serum was assessed by the appearance of C3d as well as the activation-specific protein-protein complexes C1rs-C1inhibitor (classical pathway) and C3b(Bb)P (alternative pathway). Complement was activated via both the classical and the alternative pathway in a dose- and time-dependent manner. In contrast to earlier observations, however, complement was less affected in the serum of asthmatics than in the serum of normal individuals. Differences were restricted to alternative-pathway activation, probably due to preactivation and/or a significantly higher serum concentration of the regulatory protein factor H in asthmatic patients. In vitro generation of C3a in bronchoalveolar lavage fluid could not be achieved, although the presence of alternative pathway proteins C3, B and D was demonstrated.

Allergens↗
PubMed1973

The complement system in bullous pemphigoid. I. Complement and component levels in sera and blister fluids.

Compared with other serum and blister fluid proteins, total hemolytic complement was reduced in the blister fluid of six serologically positive bullous pemphigold patients while four serologically negative cases had blister fluid complement levels closely approaching the serum levels. Except for pemphigus vulgaris blisters. blister fluids from most patients with other bullous diseases and experimentally induced blisters had blister fluid complement levels more closely approaching the serum levels. With the exception of the two terminal components. C8 and C9, individual components of the complement sequence were also reduced in the blister fluids of the six bullous pemphigold patients with circulating basement membrane zone antibodies. On the other hand, transferrin and IgG levels of these same six serologically positive blister fluids closely approached the corresponding serum levels. Conversion of C3 proactivator was also demonstrable in the serologically positive bullous pemphigoid blister fluids, but not in the corresponding sera. Our studies, therefore, are suggestive of local activation of the complement sequence, by both the classical and alternate pathways, in blisters of serologically positive bullous pemphigold patients.

Basement Membrane↗