The stabilization of the C3b molecule in immune deposits by formalin

Complement activation according to the alternate pathway by glass and plastic surfaces and its role in neutrophil adhesion

C3-deposition, generated by complement activation according to the alternate pathway, was detected on borosilicate glass slides and polystyrene Petri dishes. The C3-depositions grew peripherally until the entire surface was covered. The deposits were also visualized with scanning electron microscopy and could not be washed away with low-pH (3.5) or high-pH (9.6) buffers. No consumption of complement function was detected indicating a phenomenon restricted to the glass and plastic surfaces. The C3-deposits could mediate an adherence of human neutrophils.

Immunohistology on formol-sublimate fixed and paraplast embedded kidney tissue with comparison to formalin fixation and to pre-embedding immunofluorescent staining

Many alternative methods for immunopathological evaluation of kidney tissue are now available. Immunofluorescent or immunoperoxidase staining of kidney can be performed after formalin fixation and paraffin embedding. This is also possible after fixation with formol-sublimate (Stieve's fluid) using the immunoperoxidase technique or by immunofluorescence after removal of mercury. Reduction of strong nonspecific fluorescence caused by the mercury fixative parallels the elimination of mercury as verified by X-ray microanalysis of the sections. Using a mouse model with injection of graded dilutions of antiglomerular basement membrane antibodies, immunofluorescent staining after Stieve fixation and embedding in Paraplast was about 60% of that in cryostat sections. Immunofluorescent staining after mercury removal can be followed by silver staining for detailed morphologic study of the same 1 micron Paraplast sections. A case of antiglomerular basement membrane glomerulonephritis is illustrated in more detail to show the necessity of alternative methods, including the technique presented, pre-embedding immunofluorescent staining of Epon sections, and electron microscopy, to make a reliable diagnosis of this disease.