Complement activation by isolated myelin: activation of the classical pathway in the absence of myelin-specific antibodies

Abnormal serum factors in Guillain-Barré syndrome

The Guillain-Barré Syndrome (GBS) is generally considered to be a cell-mediated immunopathologic disease of the peripheral nervous system (PNS), although the evidence for this is indirect. Both in vitro and in vivo studies of sera from experimental animals with autoimmune demyelinating neuropathies suggest that serum factors, including antibodies to PNS myelin and/or Schwann cells, may be important in the pathogenesis of some of these disorders. More recently, similar in vitro and in vivo techniques, including the production of demyelination following intraneural injection in the rat have been employed to study sera from patients with GBS. The results of these studies demonstrate the presence of factor(s), as yet not fully characterized, that may be important in mediating demyelination. Moreover, in some patients with chronic or relapsing demyelinative inflammatory neuropathies and monoclonal gammopathy, there is evidence of antimyelin antibodies to PNS myelin. Further studies of serum from patients with acute GBS and these other neuropathies may clarify the role of serum factors in acquired inflammatory diseases of the PNS.

Multiple Sclerosis: Immunogenetic Analyses of Sib-Pair Double Case Families. II. Studies on the Association of Multiple Sclerosis with C2, C4, BF, C3, C6, and GLO Polymorphisms

The complement component polymorphisms of C2, C4, BF, C3, C6, and the enzyme polymorphism GLO were studied in 13 sib-pair double case families with multiple sclerosis. A significant association was seen between MS patients and the C4 haplotype A4,B2 as compared with their healthy siblings. This finding seems to parallel reports on C2 hypocomplementemia in MS patients since C4 A4,B2 in normal individuals was also seen to be in linkage disequilibrium with the C2 deficiency allele (C2QO) by other investigators.

In vitro complement binding on cytoplasmic structures in normal human skin: immunoelectronmicroscopic studies

We have previously provided evidence that suggests that exposure of cryostat skin sections to normal human serum (NHS) results in the antibody-independent Clq binding to cytoplasmic structures of various cell types, leading to classical complement pathway activation as evidenced by cytoplasmic C3 deposition. In the present study, we have employed immunoelectronmicroscopic methods to clarify the exact nature of cytoplasmic C3 binding structures. Incubation of cryostat skin sections with NHS followed by peroxidase-labeled rabbit anti-human C3 serum (HRP-R/Hu C3) revealed that intracytoplasmic binding of C3 occurred in suprabasal keratinocytes, melanocytes, fibroblasts, smooth muscle cells, endothelial cells, pericytes, Schwann cells, and nerve axons, but not in basal keratinocytes, Langerhans cells, and other cellular constituents of the skin. C3 binding, as revealed by the deposition of HRP reaction product, was exclusively confined to intermediate-sized filaments (ISF), which can therefore be considered to represent the subcellular site for classical complement pathway activation. Under experimental conditions that do not allow classical complement pathway activation, ISF were not decorated. Our observation that ISF of ontogenetically different cell types share the capacity of complement fixation is in accordance with the recent finding that different ISF types, despite their biochemical and antigenic heterogeneity, have common alpha-helical domains and may provide a clue to the mechanism and site of interaction between complement components and ISF.