Complement-activating Immune Complexes Research Articles

SYSTEMIC LUPUS ERYTHEMATOSUS WITH MYOSITIS OVERLAP SYNDROME IN MALE: A RARE CASE

Systemic lupus erythematosus (SLE) is an inammatory systemic disease that damages organs by depositing autoantibodies and complement-activating immune complexes or by vascular occlusion resulting from procoagulant states linked with antiphospholipid antibodies(APLA). SLE is a chronic autoimmune disorder that affects women of childbearing age in the vast majority of cases [5]. SLE is diagnosed by the presence of clinical manifestations (clinical domains) and auto-antibodies (Immunological domains). SLE is becoming more prevalent. Here, we report a rare case of a young male with SLE who presented with add-on features of inammatory myositis

Autoantibodies to myelin basic protein (MBP) in healthy individuals and in patients with multiple sclerosis: a role in regulating cytokine responses to MBP

Anti-myelin basic protein (-MBP) autoantibodies have generally been considered to be absent from sera from healthy individuals, but to be detectable in sera from some patients with multiple sclerosis (MS). However, their pathogenic role is uncertain. We demonstrate the presence of MBP-reactive autoantibodies in sera from 17 healthy individuals and 17 MS patients. The addition of MBP to the sera caused a dose-dependent deposition of MBP and co-deposition of immunoglobulin M (IgM) and fragments of complement component 3 (C3) on allogeneic monocytes. Calcium chelation abrogated the immunoglobulin deposition, indicating that formation of complement-activating immune complexes played a role in the binding process. Furthermore, MBP elicited tumour necrosis factor (TNF)-alpha and interleukin (IL)-10 production by normal mononuclear cells in the presence of serum from both patients and controls. Mononuclear cells from MS patients responded to MBP with the production of interferon (IFN)-gamma, IL-4 and IL-5, in addition to TNF-alpha and IL-10. The production of IFN-gamma and IL-5 was increased when MS serum was added rather than normal serum. Denaturation of MBP strongly inhibited MBP deposition and the MBP-induced IgM deposition and cytokine production, indicating that these events were facilitated by autoantibodies recognizing conformational epitopes on MBP. We infer that MBP-elicited TNF-alpha and IL-10 responses are promoted to equal extents by naturally occurring MBP autoantibodies and autoantibodies contained in MS sera. However, the latter seem to be more efficient in facilitating the production of IFN-gamma and IL-5.

Distinct and Separable Roles of the Complement System in Factor H-Deficient Bone Marrow Chimeric Mice with Immune Complex Disease

Plasma complement factor H (Cfh) is a potent complement regulator, whereas Cfh on the surface of rodent platelets is responsible for immune complex processing. For dissection between the two, bone marrow chimeras between Cfh-deficient (Cfh(-/-)) and wild-type C57BL/6 mice were created. Platelet Cfh protein was tracked with the Cfh status of the bone marrow donor, indicating that platelet Cfh is of intrinsic origin. In an active model of immune complex disease, Cfh(-/-) mice that were reconstituted with wild-type bone marrow had levels of platelet-associated immune complexes comparable to those of wild-type mice and were protected against the excessive glomerular deposition of immune complexes seen in Cfh(-/-) mice, yet these mice still developed glomerular inflammation. In contrast, wild-type mice with Cfh(-/-) bone marrow had reduced platelet-associated immune complexes and extensive glomerular deposition of complement-activating immune complexes, but they did not develop glomerular pathology. The large quantities of glomerular C3 in wild-type mice with Cfh(-/-) bone marrow were in the form of iC3b and C3dg, whereas active C3b remained in Cfh(-/-) recipients of wild-type bone marrow. These data show that plasma Cfh limits complement activation in the circulation and other accessible sites such as the glomerulus, whereas platelet Cfh is responsible for immune complex processing.

An anti-pso�p27 monoclonal antibody reacts with skin and peripheral blood leukocytes from Japanese psoriatic patients and shows cross-reactivity with SCCA2b

Keywords pso p27 AE Psoriasis AE Japanese descent AESquamous cell carcinoma antigenPsoriasis is a chronic inflammatory skin disease char-acterized by scaly plaques that result from epidermalhyperproliferation and infiltration of various inflam-matory cells. Although this disease was recently recog-nized as an autoimmune disorder [1], no promisingautoantigen candidates have yet been identified.Retrovirus-like particles were first identified in skinand urine from psoriatic patients in 1983 [2, 3]. In 1988,a mouse monoclonal antibody (mAb) was establishedagainst the 27-kDa detergent-soluble antigen derivedfrom the retrovirus-like particles in psoriatic patients(pso p27) [4]. We have demonstrated that the anti-psop27 mAb reacts with stratum corneum cells, some spi-nous cells and some tryptase-positive dermal infiltratingcells in skin biopsies from psoriatic patients of Europeandescent [5], and that this reactivity is diminished in skinbiopsies from patients who have undergone cyclosporineA therapy [7]. In addition, we have shown that pso p27participates in the formation of complement-activatingimmune complexes in psoriatic scales [8]. However, nostudies of the role of pso p27 had been carried out onJapanese patients with psoriasis. Moreover, in a proteindatabase search we found homology between apublished N-terminal protein sequence of pso p27 [6]and a squamous cell carcinoma antigen (SCCA)belonging to the serpin protease inhibitor family [9].In this study, we used immunofluorescent microscopyto examine the reactivity of the anti-pso p27 mAb withskin and peripheral mononuclear cells from Japanesepatients with psoriasis. We isolated recombinant SCCAfrom a cDNA library made using human keratinocyteRNA and examined the reactivity of the clones withanti-pso p27 antibody.Skin sections of 2–4

Characteristics of a novel low affinity complement C3dg-binding protein of human platelets.

The breakdown products of the complement protein C3 function in receptor-mediated immune clearance. The catabolism of the C3 molecule, mediated by factors I and H, results in the generation of the fragments C3c and C3dg. C3dg binds to human platelets in a specific and saturable manner. The direct interaction of platelets with soluble C3dg may contribute to immune-mediated platelet destruction. More importantly, platelets may interact with opsonized pathogens or complement-activating immune complexes via C3dg. In this report, we investigated the interaction of C3dg with platelets and calculated the Ka to be 3.2 x 10(6) M-1 with 1100 to 2200 specific binding sites/platelet. In the presence of 5 mM calcium, both the Ka and the number of specific binding sites were modestly decreased to Ka = 2.8 x 10(6) M-1 with 1400 to 2400 specific binding sites/platelet. The Scatchard plots demonstrated a curvilinear character. On labeling C3dg with peroxidase and visualizing platelet-bound C3dg by electron microscopy, it was shown that binding sites for C3dg were restricted to the platelet plasma membrane. Using a cell attachment assay, platelet adhesion to C3dg was readily detectable; attachment to C3dg-coated plates was not blocked by fibrinogen or fibronectin. We have characterized the C3dg-binding protein of platelets using the chemical cross-linkers, SASD and DSS, to cross-link C3dg to thrombin-stimulated platelets. Gel filtration of the 125I-labeled C3dg-platelet complex revealed the presence of a large protein complex that was absent when 125I-labeled C3dg alone was analyzed. SDS-PAGE of the radiolabeled cross-linked protein, followed by autoradiography, identified a 95-kDa membrane protein. The relationship of this C3dg-binding protein to other platelet membrane proteins has yet to be determined.

The Expression of Retrovirus-Like Particles in Psoriasis

Retrovirus-like particles have been isolated from patients with psoriasis. Antigens crossreacting with the major internal proteins pso p27, of these particles have been demonstrated in the wall of dermal vessels and in a subfraction of cells in psoriatic lesions. The antigen has also been observed in blood lymphocytes from psoriatic patients. Pso p27 antigen and anti-pso p27 antibodies are present as complement-activating immune complexes in psoriatic scale and in the blood of patients with psoriasis and psoriatic arthritis. The potential contribution of the circulating immune complexes to the inflammatory process in psoriasis is discussed.

Immune complexes and complement activation following rupture of intracranial saccular aneurysms.

Circulating immune complexes (CIC) and complement activation (plasma C3d levels) were monitored during a 2-week period in patients with ruptured cerebral aneurysms and also in patients with cerebral hematoma unrelated to saccular aneurysms. Thirteen of 18 aneurysm patients were found to have CIC on admission as compared to three of 21 healthy blood donors (p less than 0.001). The presence of CIC in aneurysm patients was associated with a poor prognosis. Eight of nine patients who developed angiographic vasospasm had CIC on admission compared with one of four without vasospasm. Patients with vasospasm showed a twofold increase in plasma C3d levels at the time when the spasm occurred, whereas no significant changes in the C3d concentration could be demonstrated in aneurysm patients without spasm or in patients with hematoma unrelated to aneurysm rupture. These findings suggest that immunological processes involving complement-activating immune complexes are involved in the pathogenesis of cerebral vasospasm following rupture of saccular aneurysms.

G6PD-deficiency infectious haemolysis: a complement dependent innocent bystander phenomenon.

Dramatic haemolysis may accompany viral hepatitis and pneumococcal pneumonia in G6PD-deficient patients. Since red blood cells (RBCs) are richly endowed with receptors for activated complement, particularly C3b, we hypothesized that bulky, complement-activating immune complexes (IC) consisting of microbes and antibody might attract granulocytes (PMNs), facilitating oxidative 'innocent bystander' RBC damage. Indeed, opsonization with only two type-2 pneumococcus (PN3)/anti-PN3/C3b complexes per RBC caused agglutination of RBC, a phenomenon termed immune adherence. Addition of as few as one PMN per 20 opsonized RBCs caused the glutathione (GSH) levels of co-incubated G6PD-deficient RBCs to fall by 30% (from 3.5 to 1.8 +/- 0.8 mumoles GSH/g Hb) compared to identically incubated, but nonopsonized, G6PD-deficient RBCs. GSH levels remained normal (5.2 +/- 0.4 mumoles/g Hb) in PMN-exposed opsonized normal RBCs. GSH depletion in G6PD-deficient RBC was directly related to disease severity--falling a mean 33% in RBCs from two Black G6PD A- subjects but 59% in two Caucasian G6PD deficient RBCs. Prevention of C3b generation (with 10 mM EDTA) during opsonization abrogated both immune adherence and PMN-mediated GSH decline in oxidant-sensitive cells. Similarly, removal of C3b receptors by brief trypsin incubation of RBCs eliminated immune adherence and GSH decline. Thus, both phenomena are dependent on IC complement activation and subsequent binding of the bacterial IC to the RBC complement receptors. Although clearance of IC by RBCs may be beneficial in protecting other tissues from inflammatory damage, G6PD-deficient RBCs are vulnerable to oxidants generated by juxtaposed phagocytes--cells attracted to, and stimulated by, the immune complex/C3b combination. It is suggested that this 'Good Samaritan' activity of RBCs may lead to haemolysis during periods of exuberant antibody response to microbes.

Evidence Supporting a Role for Immune Complex-Mediated Inflammation in the Pathogenesis of Bullous Lesions of Systemic Lupus Erythematosus

Evidence supporting an immune complex pathogenesis of bullous lesions in systemic lupus erythematosus includes immune deposits, acute inflammation, and blister formation at the cutaneous basement membrane zone. Since cutaneous immune deposits are a general feature of lupus, an attempt has been made to determine whether deposits in lupus patients with blisters are functionally different from those in patients without blisters. Skin was obtained from 4 consecutive patients with blisters and 14 controls. The groups were matched for clinical and serologic features, duration and activity of disease, and treatment. Skin was examined by direct immunofluorescence for immune deposits and by the leukocyte attachment assay for quantification of complement-activating immune complexes. Clinically normal, viable skin from 1 patient with blisters and 1 patient without blisters was incubated in organ culture with normal human leukocytes and serum complement. All patients in both groups had immune deposits at the basement membrane zone with an equivalent incidence of the major Ig classes. Deposits in patients with blisters were slightly more intense and a linear pattern of fluorescence seen in 75% of these patients was not seen in controls. The leukocyte attachment assay showed significantly greater (p less than .02) cell attachment in patients with blisters (mean = 167) than in patients without blisters (mean = 64) and greater cell attachment in peribullous than normal skin from the same patient. Organ culture showed complement-dependent migration of leukocytes and histologic features similar to those in spontaneous lesions in skin from the patient with blisters but not in skin from the patient without blisters. These results provide evidence supporting immune complex and complement-dependent inflammation in the pathogenesis of bullous lesions in systemic lupus erythematosus.

Natural Antibodies against a Polysaccharide (Bo) from Sugar Cane Mediate its Complement-Activating Effect

The interaction of a complement activating glucan from sugar cane (Bo) with immunoglobulins was studied. Bo precipitates a small fraction of IgG from human serum. In combination with this fraction, it activates complement by the classical pathway, not in its absence. Bo is adsorbed to and can be eluted from Sepharose containing covalently coupled IgG; it is not bound when the IgG-Sepharose is lacking the Bo-reactive IgG fraction. Bo-IgG complexes activate and fix {ie110-1}. The binding of {ie110-2} to aggregated IgG is not inhibited by Bo. This is in contrast to the strong inhibition of {ie110-3} fixation by the Fc-binding protein A. It is concluded that normal human serum contains natural antibodies against Bo which form complement-activating immune complexes with Bo by binding it to their F(ab) region. The antibodies do not cross-react with dextran, a glucan from barley, nor with surface constituents of E. coli.

Functional Evidence for Complement-activating Immune Complexes in the Skin of Patients with Bullous Pemphigoid

Previous immunofluorescent studies showing deposits of immunoglobulin and complement at the cutaneous basement membrane zone have provided evidence supporting a role for immune complexes in the pathogenesis of bullous pemphigoid. In this study the functional activity of the deposits has been examined using leukocyte attachment, a method for detecting and quantitating the biological activity of complement-activating immune complexes in tissues. When peripheral blood leukocytes suspended in serum complement were incubated with cryostat sections of lesional and adjacent normal-appearing skin from 9 patients with pemphigoid, skin from 11 normal controls and lesional skin from 14 nonpemphigoid disease controls there was significantly greater attachment of leukocytes to the basement membrane zone of lesional bullous pemphigoid skin compared to normal-appearing pemphigoid skin and skin of both control groups. A significant reduction in attachment in the absence of serum complement suggested the reaction was dependent on activation of complement by tissue-deposited complexes. Although leukocyte attachment was greater in lesional than normal-appearing pemphigoid skin, a comparison of the incidence and intensity of cutaneous IgG and complement immunofluorescence between the 2 groups showed no significant differences. Furthermore, no correlation between leukocyte attachment and serum titers of immunoglobulin G or complement-binding anti-basement membrane zone antibodies was observed. These results suggest that immune reactants in lesional pemphigoid skin are functional complement-activating immune complexes, that differences exist between the activity of complexes in lesional and normal-appearing pemphigoid skin and may explain why lesions develop at some sites and not others.

Functional Evidence for Complement-activating Immune Complexes in the Skin of Patients with Bullous Pemphigoid

Functional Evidence for Complement-activating Immune Complexes in the Skin of Patients with Bullous Pemphigoid

Inactivation or elimination of potentially trypanolytic, complement-activating immune complexes by pathogenic trypanosomes.

Trypanosoma brucei subsp. brucei and T. congolense incubated in homologous antibody at 0 degrees C for 30 min were lysed by subsequent addition of guinea pig complement. Trypanosomes incubated in antibody at 37 degrees C before complement treatment remained intact. Parasites bearing adsorbed antibody also remained intact when incubated at 37 degrees C before complement treatment. The proportion of cells which survived complement treatment decreased with increasing antibody concentration. Parasites which survived complement treatment continued to express antigens which could bind complement-activating antibody, but did not bear complement-activating immune complexes. Virtually all cells in T. brucei populations exposed to antibody at 37 degrees C, but only 10(-3) to 10(-5) of the cells in populations exposed to antibody at 0 degrees C before complement treatment, remained infective for X-irradiated mice. Only 10(-6) to 10(-7) of T. brucei populations exposed to antibody at 0 or 37 degrees C before complement treatment infected mice immunized with homologous antigens. Serotype analysis of substrains and of T. brucei populations isolated from mice infected with antibody and complement-treated parasites suggested that variant-specific antigens participated in trypanolysis and that T. brucei which survived complement treatment could undergo antigenic variation. Mechanisms by which trypanosomes may inactivate or eliminate surface immune complexes and the possible significance of this phenomenon in trypanosomiasis are discussed.