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Immunoglobulins and C3 were detected by immunofluorescence in the blood vessel walls of biopsies of clinically normal skin in patients with active necrotizing vasculitis. Of the 13 patients studied, 9 had C3 and 6 of these had IgM or IgA in biopsies of lesions of vasculitis. In adjacent clinically normal skin, 7 patients had C3 and 3 of these also had IgM or IgA. These findings support the hypothesis that immunoglobulins and complement are present in vessels of some patients prior to chemotaxis of polymorphonuclear leukocytes and the resulting inflammatory purpuric lesions so characteristic of necrotizing vasculitis.

In this study, an in vitro model of immune complex-mediated basement membrane zone separation caused by periphigoid antibodies, serum complement, and peripheral blood leukocytes is described. When cryostat sections of fresh-frozen normal human skin were treated with either of 4 bullous pemiphigoid sera containing complement-activating anti-basement membrane zone antibodies and subsequently incubated at 37 degrees C with normal human peripheral blood leukocytes and fresh human serum, leukocytes attached to 96% of the basement membrane zone in 100% of sections. Sixty-seven percent of the sections developed focal areas of basement membrane zone separation resembling dermal-epidermal separation described in early pemphigoid lesions. In control sections in which either leukocytes, pemphigoid antibody or fresh human serum were omitted, significantly less leukocyte attachment and basement membrane zone separation occurred. Evidence that leukocytes caused separation was supported by an absolute requirement for viable leukocytes during incubation, a high correlation between leukocyte attachment and separation and experiments showing that leukocytes attached to the basement membrane zone were activated. This study provides the first in vitro evidence directly supporting a functional role for immune-complex mediated inflammation in the pathogenesis of basement membrane zone separation and blisters in bullous pemphigoid.

To study the mechanisms responsible for leukocytoclastic vasculitis, we evaluated the kinetics of immunologic and cellular changes in induced vasculitis lesions. In four of five consecutive patients with active vasculitis, lesions were induced by increasing vascular permeability via injecting histamine into the skin. Biopsies were obtained for light and electron microscopy and immunofluorescence at 1, 4, 8, and 24 hr after injection. The results show that immunoglobulin, C3, and electron-dense material are deposited in vessel walls early and are followed by cellular infiltration. The characteristics of the cellular infiltrates were quite diverse at different times after histamine provocation and no distinctive patterns were seen. Nevertheless, the kinetics of the appearance of immunoreactants and cells implies that immunoglobulin and probably circulating immune complexes are present prior to the development of inflammation and supports the contention that deposition of immune complexes within vessel walls is responsible for leukocytoclastic vasculitis.

MNL cellular chemotaxis, bacterial killing and phagocytosis, and Oil Red O phagocytosis were studied in vitro in the presence of eight anti-inflammatory or immunosuppressive drugs. Inhibition of Boyden Chamber migration of MNL's in a MNL-lymphocyte mixture was achieved after 1/2 hr incubation by 10(-3) and 10(-4) mol/L. concentrations of chloroquine (maximum inhibition 63% +/- 2.8), dexamethasone (58% +/- 8.6), 6-mercaptopurine (62% +/- 4.2), methotrexate (66% +/- 6.4), and vinblastine (100%). Bacterial killing was not significantly affected by any of the drugs studied. Bacterial phagocytosis was improved by vinblastine at 10(-3) and 10(-4)M and by 6-mercaptopurine at 10(-5)M, but there was apparent interference with the assay at high drug concentrations. Modification of the Oil Red O technique showed inhibitions of MNL phagocytosis by vinblastine at 10(-3)M (69% +/- 2.8 inhibition), chloroquine at 10(-3)M (49% +/- 8.5), and mercaptopurine at 10(-3)M (32.5% +/- 0.7). Cyclophosphamide, although reported to require hepatic conversion in vivo, may be partially activated in a lymphocyte-MNL mixture in vitro, producing a decrease in cell viability but no statistically significant impairment of MNL function. These results support direct inhibition of MNL cellular function as one of the mechanisms of the anti-inflammatory action of chloroquine, dexamethasone, methotrexate, 6-mercaptopurine, and vinblastine.

beta 1H-globulin is a recently characterized plasma protein which regulates the biologic activities of the major fragment of the third complement component, C3b. The major function of this protein is to act as a co-factor for C3b Inactivator (C3bINA) in the cleavage of C3b to an intermediate molecule, C3b', consisting of an intact beta-chain covalently bound by disulfide bridges to 2 alpha-chain fragments of 40,000 and 67,000 daltons. Final cleavage of C3b' to the C3c and C3d fragments requires an additional protease such as plasmin or elastase. Additionally, beta 1H interferes with the activity of the alternative pathway convertases, C3bBb and C3bBbP, by displacing or competing with the binding of factor B. In this study, perilesional skin biopsies from 10 patients with active bullous pemphigoid were examined for the presence of beta 1H at the dermal-epidermal junction by immunofluorescent methods. The protein was found in 8 of 9 biopsies in which C3 also was deposited. In a single case where C3 was not found, beta 1H was not seen. These findings suggest that beta 1H plays a role in the in vivo control of C3b and provides additional evidence for the participation of the complement system in the pathogenesis of bullous pemphigoid.

It has been proposed that cutaneous inflammation and blister formation in bullous pemphigoid is caused by antibodies to the cutaneous basement membrane zone which active complement, thereby, attracting leukocytes to the dermal-epidermal junction. There is, however, no functional evidence which supports a role for pemphigoid antibodies in complement activation or leukocyte activity in skin. This study describes the in vitro attachment of human peripheral blood leukocytes to the dermal-epidermal junction of cryostat skin sections treated with 9/13 pemphigoid sera containing antibodies to the cutaneous basement membrane zone. A requirement for complement in the reaction was supported by the findings that only complement-fixing pemphigoid sera mediated the leukocyte response, a strong correlation existed between complement-fixation titers and leukocyte attachment titers and only leukocytes suspended in fresh serum but not buffer or heat inactivated serum attached at the junction. A requirement for antibody was supported by the observation that IgG fractions of 4 pemphigoid sera were as effective as whole sera in mediating leukocyte attachment. The leukocyte response was shown to be specific for complement-fixing pemphigoid sera since it was not observed with noncomplement-fixing sera or sera from 15 normal human and 22 nonpemphigoid disease controls. This study offers functional evidence for an interaction between pemphigoid antibody, complement and leukocytes in the immunopathogenesis of bullous pemphigoid and demonstrates that complement-fixing antibasement membrane zone antibodies may be important in initiating the cellular inflammatory events observed near the dermal-epidermal junction in vivo.

Human hypersensitivity angiitis is an immune complex disease in which patients present with palpable purpuric lesions of the skin and may often have multiple organ involvement. The antigen may be derived from an infectious organism such as the hepatitis virus, streptococcus, or a drug, and complexes with antibody. Under circumstances of vascular turbulence or vessel wall dilatation this complex may become fixed, activating the complement sequence with elaboration of chemotactic factors for neutrophils. These cells release lysosomal enzymes resulting in vessel wall destruction. Red blood cells leak into the tissue producing purpura and the inflammatory infiltrate accounts for the palpability. Although many patients have skin lesions only, others may have involvement of joints, gastrointestinal tract, kidneys, and even the lungs. The central question in the pathogenesis of this disease is why the immune complex is so selective in its site of deposition. Part of the reason must be related to the lattice formation of a particular complex, while other reasons are related to host factors of altered vascular permeability, integrity of clearance mechanisms or even a genetically determined defect of the phagocytic system.

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.

Hypersensitivity angiitis is a disease in which patients present with palpable purpura dominant on the lower legs. As lesions evolve they become confluent, and sometimes hemorrhagic and ulcerate. Other organ systems may be involved, particularly the joints, gastrointestinal tract, and kidneys. Current evidence supports an immune complex pathogenesis in which a variety of antigens including bacteria, viruses, drugs, or chemicals are involved. Therapy consists of identifying the potential offending agent and administration of antiinflammatory drugs.