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PubMed1986

Functional analysis of activated C1s, a subcomponent of the first component of human complement, by monoclonal antibodies.

Three mouse monoclonal antibodies (M365, M81, and M241) directed against human C1s were used to analyze the structure of C1s related to the enzymatic activity. M365 and M81 recognized different epitopes on the heavy chain of C1s and could bind to C1s, as well as to C1s. The C4 cleaving activity of C1s was completely blocked by M81 and was partially blocked by M365. Although the C2 cleaving activity of C1s was partially inhibited by M81, no blocking was observed with M365. Both antibodies had no effect on the esterolytic activity of C1s. These results indicate that the C4 and C2 binding sites on C1s reside in the heavy chain, and they are distinct from each other. M241 could bind only to C1s, an active form of C1s. After reduction of C1s, M241 could not react with either heavy or light chain of C1s. The esterolytic activity of C1s was markedly reduced by M241. Furthermore, M241 blocked not only the cleavage of C4 and C2 by C1s but also the complex formation of C1s and C1 inactivator. From these observations, we suggest that M241 reacts with the active site of C1s, and both heavy and light chains of C1s participate in the composition of the active site.

Antibodies, Monoclonal↗
PubMed1989

Studies on contact activation: effects of surface and inhibitors.

Contact activation is initiated when the plasma proteins, Hageman factor (factor XII), prekallikrein and high molecular weight kininogen interact with negatively charged materials. The activation of the intrinsic pathway of blood coagulation and the production of bradykinin are among the sequelae of contact activation. The kinetics of the activation of the contact system are modified by plasma inhibitors, C1 inhibitor being quantitatively the most important. We propose that the activation of the system requires that the stimulus provided by the surface must be greater than a threshold value to overcome the effects of the inhibitors. We show in this paper that the amount of surface required for activation is much reduced in the absence of C1 inhibitor (Hereditary Angioedema) or in the cold where the inhibitor loses much of its effectiveness. Antithrombin III inhibition of activated Hageman factor is augmented by heparin which is also an activator of Hageman factor. The rate constants for inhibition remain much lower than for C1 inhibitor, however.

Antithrombin III↗
PubMed1989

[A case of hereditary angioneurotic edema associated with systemic lupus erythematosus].

A 33-year-old woman noticed recurrent and sudden attacks of subcutaneous swelling of the extremities and face since the age of 4 years. Sometimes the attacks involved colicky abdominal pain. Her mother and younger sister had episodes of recurrent swelling of the extremities as well. Complement studies revealed low CH50, C1q, C4, and C1 inhibitor levels, with normal C3 and C5 levels. Similar reductions of CH50 C4 and C1 inhibitor levels were observed in her mother, older, and younger sisters. Therefore, she was diagnosed as hereditary angioneurotic edema. In addition, she was diagnosed as having a butterfly rash at the age of 20 years and had a history of solar sensitivity. Histologically the facial lesion showed liquefaction degeneration of the basal cell layer. Direct immunofluorescent staining of the affected skin lesion showed basement membrane-zone staining of IgG and IgM. Laboratory studies revealed lymphopenia and positive ANF. On the basis of the above findings, hereditary angioneurotic edema associated with systemic lupus erythematosus was diagnosed.

Adult↗
PubMed1989

[Serum complement composition of myasthenia gravis].

Serum complements of C1q C1, C4, BF, C1-INH and C5 were measured by single immunodiffusion in 54 patients with myasthenia gravis (MG), 46 normal control (NC) and 42 cases of other neurological disorders. It was found that C1-INH, C5 levels in MG were significantly higher than that in other groups (P less than 0.01). The serum levels of C1-INH, C5 were not related to the clinical type and the stage of the illness. These data suggest that endplate receptors might be disrupted through complement mediated immunoreaction.

Adult↗
PubMed1989

Terminal complement complexes and C1/C1 inhibitor complexes in autoimmune thyroid disease.

The potential role of complement activation and the membrane attack complex in the pathogenesis of Graves' disease and Hashimoto's thyroiditis has been investigated by measuring serum concentrations of the C1r-C1s-C1 inhibitor complex (C1/C1-inh) and the terminal complement complex (TCC), and by studying the binding to thyroid tissue of monoclonal and polyclonal antibodies against TCC neoantigens. Serum C1/C1-inh and TCC concentrations were significantly increased in 29 patients with untreated Graves' disease compared with 47 healthy subjects (P less than 0.001 for both), and decreased significantly after carbimazole treatment in 18 of these patients for whom post-treatment samples were available (P less than 0.01 and P less than 0.02, respectively). The serum TCC concentration, but not that of C1/C1-inh, was also significantly increased in 15 patients with Hashimoto's thyroiditis compared with the 47 healthy subjects (P less than 0.001). TCCs were identified by immunohistochemical staining around the thyroid follicles in thyroidectomy specimens from patients with Graves' disease (six out of six) and Hashimoto's thyroiditis (two out of two); normal thyroid tissue from two subjects showed no staining. These results suggest a role for complement, in particular the membrane attack complex in the pathogenesis of autoimmune thyroid disease.

Adolescent↗
PubMedDate not supplied

[Hereditary angioedema. Effect of danazol on C4 and functional C1INH].

Hereditary angioedema (HAE) is an inherited deficiency of the inhibitor of C1 esterase (C1 inh). Two types of genetic C1 inh deficiency have been described, type I: quantitative, and type II: functional. For the purpose of the present study, 4 out of 51 HAE patients were selected. None of them had received any previous androgenic therapy. The group was integrated by two type I and one type II cases. All patients that entered in the protocol received 400 mg/day of danazol over 14 days. The complement system was evaluated by monitoring C4, Hemolytic complement 50% (CH50), Circulating Immune Complexes (CIC), and antigenic and functional C1 INH during the study. The level of the complement factors at the beginning and the end of this period demonstrated a statistically significant increase of C4 and CH50 and the disappearance of CIC, while C1INH remained unmodified. These results suggest that the therapeutic effect of Danazol may have two mechanisms of action: i. promotion of C4 synthesis by anabolic effect resulting in an improvement of the complement system with the disappearance of CIC, and ii, a minor increase of C1 inh level primarily due to the lack of its consumption.

Adult↗
PubMed1989

[A case of hereditary angioneurotic edema provoked by functional insufficiency of C1-inactivator].

The hemolytic activity of complement, the concentration of C1-inactivator, of C1q and C4 components of complement as well as the activity of contact-activated kallikrein and the functional activity of C1-inactivator were studied in the plasma of a female patient with hereditary angioneurotic edema (HAE), of her mother, sister and normal donors. The hemolytic activity of complement, the concentration of C1-inactivator and C1q in the blood plasma of the persons examined turned out unchanged as compared with the same parameters in donors. Meanwhile in the patient with HAE and her mother with symptoms similar to HAE, the concentration of C4 appeared lower than that in the patient's sister not suffering from the disease and in donors. The activity of contact-activated kallikrein in the plasma of the patient's sister and mother exceeded the activity of the enzyme in donors. The least activity of plasma kallikrein was recorded in the proband. The functional activity of C1-inactivator in the proband constituted 50-60% of the activity of that parameter in her sister and donors. The magnitude of the functional activity of C1-inactivator in the patient's mother approximated its magnitude in the proband. Therefore, the development of HAE in the given case was mainly provoked by functional insufficiency of C1-inactivator. The magnitude of the spontaneous TAME-esterase kallikrein-like activity in the blood plasma of the patient with HAE remained within normal.

Adult↗
PubMed1989

Spontaneous activation of reconstituted and serum C1 and the role of C1-inhibitor.

Evidence will be presented that first order, spontaneous activation of solution C1 at 37 degrees C under physiological conditions is a very slow process with a half-life of the order of one day and perhaps considerably longer. In addition, negative evidence will be presented showing that the formation of functionally significant levels of a complex between C1-Inhibitor and unactivated C1 does not occur. Such a complex had been previously postulated to explain the strong inhibition of the spontaneous activation of C1 which was observed upon the addition of C1-Inhibitor. Rather, we shall demonstrate that C1 catalytically activates C1, and that a critical role for C1-inhibitor is to complex with C1 to eliminate this autocatalytic reaction.

Catalysis↗
PubMed1989

[Hereditary angioedema].

Hereditary angio-oedema (AOH) is a familial affliction that is most often hereditary, but sometimes acquired and linked to a deficiency of C1 esterase inhibitor. 8 cases have been examined, amongst which there was one attack in a young girl, without any clinical signs. Amongst the other 7, one had acquired AOH. The diagnosis was confirmed by the deficiency of C1 esterase inhibitor, associated with a significant reduction of the other fraction of complement c3-c4 and also total haemolytic complement. Strong doses of corticosteroids were used in 4 patients for urgent treatment. Basic treatment with DANAZOL was commenced in 3 patients.

Adolescent↗
PubMed1985

Cleavage of the second component of complement by plasma proteases: implications in hereditary C1-inhibitor deficiency.

EDTA plasma from patients with hereditary angioedema (HAE), the genetic deficiency of C1-inhibitor, when incubated at 37 degrees produces a kinin-like activity which can induce contraction of oestrus rat uterus. The second component of complement (C2) has previously been suggested to be the source of this kinin-like activity, with the implication that C2-kinin is a normal product of complement activation. Our results show that purified human C2 is cleaved rapidly to C2a and C2b when added to HAE plasma, but not normal plasma or plasma from a danazol-treated HAE patient. However, the addition to HAE plasma of C2 at 20 X normal plasma concentration had no effect on the kinin activity generated on incubation at 37 degrees. In the presence of soya bean trypsin inhibitor, the rate of C2 cleavage and products were unaltered but no kinin activity was generated. C2 was cleaved by purified C1s to C2a and C2b. Incubation of C2 with trypsin resulted in cleavage to C2a and C2b followed by more extensive cleavage of both C2a and C2b. Kallikrein cleaved C2 to C2a and C2b but plasmin had no effect on C2. In no case was kinin activity generated. When C2 was cleaved by C1s to C2a and C2b then incubated with trypsin, kallikrein, or plasmin, no kinin activity was generated: only trypsin cleaved the C2 fragments further. The results suggest that C2 is not the source of the kinin-like activity generated in hereditary angioedema plasma.

Angioedema↗
PubMed1987

Antibody-independent activation of C1. II. Evidence for two classes of nonimmune activators of the classical pathway of complement.

Nonimmune activation of the first component of complement (C1) by cardiolipin (CL) vesicles present specific features which were not demonstrated on immune complexes. CL vesicles which activate C1 in the presence of C1-inhibitor (C1-INH) were found to bind C1s in the absence of C1r, and to induce a specific C1r-independent cleavage of C1q-bound C1s. Therefore, several known natural nonimmune activators were analyzed by comparing their ability to activate C1 in the presence of C1-INH and to mediate a C1r-independent cleavage of C1s. Freshly isolated human heart mitochondria (HHM) activated C1 only in the absence of C1-INH. However, mitoplasts derived from HHM (HHMP) activated C1 regardless of the presence of C1-INH, and induced a specific cleavage of C1q-bound C1s. The same pattern was observed in the case of smooth E. coli and a semi-rough E. coli strain. DNA, known to activate C1 only in the absence of C1-INH, does not induce C1s cleavage in the absence of C1r. Thus, nonimmune activators can be classified into two distinct categories. "Strong" activators, such as CL vesicles, HHMP, or the semi-rough E. coli strain J5 can activate C1 in the presence of C1-INH. By using C1qs2 as a probe, they exhibit a specific, C1r-independent cleavage of C1s. C1s-binding to C1q is a critical factor for the activation process in this group. In the case of "weak" activators, such as E. coli smooth strains, DNA, or HHM, no C1s-binding to activator-bound C1q was detected, and C1r-independent C1s cleavage and C1 activation in the presence of C1-INH were not observed. As in the case of immune complexes, C1r activation appears to play a key role in the C1 activation by "weak" activators.

Calcium↗
PubMed1977

An investigation of the complement system in patients with periodic disease (results from 29 cases).

The complement system was investigated in 29 patients suffering from authentic periodic disease. A statistically significant increase in C4, also in total complement and C3 could be demonstrated. It is possible that the increase in C4 was due to the macrophages which are always present in the infiltrates of periodic disease. This biological observation is of clear practical importance for the diagnosis of the condition both before and after colchicine therapy.

Complement C1 Inactivator Proteins↗