Visualization of natural autoantibody polyreactivity by rotary metal-shadowing electron microscopy

Immunoglobulin structure and function as revealed by electron microscopy

Electron-microscopic (EM) analysis preceded crystallographic analysis [1,2] of Igs by over a decade and was for a time the only direct way of analyzing their 3-D molecular structure. Once the X-ray structures were deduced, the role of EM gradually shifted from gross structural analysis to the addressing of more sophisticated structural and functional questions. EM remains a vital adjunct to the many physicochemical, biochemical, and serological tools brought to bear on these remarkable molecules as we try to relate form to function. In this review I will highlight some of the many contributions that have been made possible by virtue of being able to 'see' Ig molecules and immune complexes.

Identification of a region responsible for binding to the cell wall within the S-layer protein of Clostridium thermocellum

The protomer forming the S-layer of Clostridium thermocellum was identified as a 140 kDa protein which was non-covalently bound to the cell wall. Cloning and sequencing of the corresponding gene revealed an open reading frame of 3108 nucleotides encoding a polypeptide of 1036 amino acids, termed SlpA. The amino acid composition of SlpA matches the composition of a previously described exocellular glycoprotein. SlpA shared extensive similarity with the S-layer protein of Bacillus sphaericus and with the outer wall protein of Bacillus brevis. In addition, the amino-terminal region of SlpA contained a segment presenting similarities with segments termed SLH (S-layer homologous), which are found in several bacterial exoproteins. A polypeptide of 209 residues comprising this segment was shown to bind to cell walls extracted from C. thermocellum cells.

A possible paradox in the immunology of multiple sclerosis: its apparent lack of 'specificity' might provide clues to the etiology

As a further development from an earlier hypothesis, a pathogenic role of polyspecific natural, idiotypically connected antibodies is claimed, that recognize concomitantly a variety of CNS antigens and are matured to some degree to higher-affinity anti-CNS antibodies without ever losing their network association. On that basis, nitrophenol-carrier conjugates well-known to be foreign target antigens of natural antibodies and present in food commodities that have epidemiological links to MS, are considered as paradigmatic for agents of possible etiologic importance.