In vitro studies with Modoc virus in Vero cells: plaque assay and kinetics of growth, neutralization, and thermal inactivation

A sensitive and quantitative assay system is described for plaquing Modoc virus in Vero cells. Neutralizing antibodies to Modoc virus could be detected by using this in vitro system by their interference with viral plaque formation. Virus was readily neutralized within 30 min at 37 C by a 1:10 dilution of hyperimmune hamster serum. The rate of neutralization and the total amount of virus neutralized was not altered significantly by the addition of 20 U of guinea pig complement to the hyperimmune hamster serum. A study of the growth of Modoc virus in Vero cells is also presented. After an initial latent period of 20 h, viral titer increased exponentially for 20 h. By 83 h after infection, 8,000 plaque-forming units of virus were detected per cell. The stability of viral infectivity in phosphate-buffered saline at pH 7.4 was evaluated. No reduction in viral titer was detected after 3 days at 7 or 22 C. A continuous decrease in infectivity at 37 C was observed, however, throughout the observation period.

Complement activation in pemphigus vulgaris blister fluid

Total haemolytic complement was reduced in blister fluids of four pemphigus vulgaris patients when compared to serum complement levels and other serum and blister fluid proteins. Complement levels in most control blister fluids, on the other hand, more closely approached their corresponding serum levels. Haemolytic C1, C4, C2, C3 and C5, measured in two pemphigus sera and blister fluids, were not measurable in one blister fluid and were extremely low in the second patient. C3 proactivator (C3PA) was absent from both of these blister fluids. Three of the blister fluids exhibited anti-complementary activity when tested with normal human serum. By adding one blister fluid to normal human serum, inhibition of haemolytic C1, C2, C3 and C5 with conversion of C3 and C3PA occurred. Activation of complement locally in pemphigus blister fluids would suggest a pathogenetic role for complement in this disease.

Mesangial cells in membranous glomerulonephritis

Renal biopsies of seven patients with membranous glomerulonephritis were examined by light, electron, and immunofluorescence microscopy. All had characteristic changes of glomerular basement membranes, typically with bright granular membranous fluorescence of IgG and variable deposits of complement. Cellularity was normal or slightly increased due largely to mesangial cell proliferation. These cells assumed a variety of appearances referred to as resting, hyperactive, and dark. Resting forms occurred in cases with normal cellularity and limited complement deposition. Hyperactive cells showed ultrastructural evidence of increased secretory and digestive activity and were associated with proliferation and more pronounced complement deposition. Dark cells, interpreted as undergoing shrinkage and degeneration, were found in small numbers in all biopsies.

Recurrent haematuria and mesangial IgA deposition

Six patients are described in whom recurrent haematuria was associated with IgA deposits in the glomerular mesangium. These patients conform closely to the nephropathy described by Berger. The condition can only be definitely diagnosed by immunofluorescence techniques. These six patients were diagnosed in one renal unit within 18 months and, despite the absence of reports from British units, this nephropathy is probably not uncommon. No treatment for it is known at present but the prognosis appears to be good in most patients. Renal failure and hypertension have been reported and long-term follow up is necessary to clarify the natural history of the disease.

Glomerular deposition of properdin in Henoch-Schönlein syndrome and idiopathic focal nephritis

Biopsy of renal tissue from four patients with idiopathic focal nephritis and three patients with Henoch-Schönlein syndrome showed that C3 and properdin were deposited with IgA in the glomerular mesangium, C1q could not be detected. These observations suggest that glomerular injury in disorders characterized by mesangial deposits of IgA and C3 is mediated via the properdin system.

The membrane attack mechanism of complement. Reversible interactions among the five native components in free solution

Reversible interactions in free solution were demonstrated to occur (a) between C5 and C8, (b) between C5, 6, 7 and C8, and (c) between C8 and C9. No interaction was observed between C8 and C6 or C7 and between C9 and C5, 6, 7. Interactions between C8 and C9 were enhanced at lowered ionic strength (0.05) and a molar excess of C8 over C9. Complex formation was independent of pH over the range of 6.5-8.5. Under optimal conditions the C8, 9 complex had a sedimentation coefficient of 10.2-10.6S, while native C8 and C9 sedimented at 8.5 and 4.8S, respectively. Specificity and reversibility of these interactions were established. In spite of the limited number of interactions observed, all five of the native proteins of the membrane attack mechanism interacted to form an association product that sedimented at 10.8-11.2S. Demonstration of this product in free solution supports the concept that C5-9 on acquisition of cytolytic activity assemble into a stable multimolecular complex.