Effect of Incubation With Rabbit Serum on Toxicity and Tumor-Necrotizing Action of Polysaccharide From S. marcescens

Abstract

Effect of incubation with rabbit serum on the lethality and tumor-necrotizing activity of two pyrogenic polysaccharide preparations was studied in mice carrying i.m. implants of sarcoma 37. The polysaccharide materials were isolated from the same strain of S. marcescens, but were prepared in different laboratories and obtained by different methods. One preparation was a crude, insoluble fraction containing protein, the other was a soluble, trypsin-digested material giving negative protein color tests. Incubation in serum reduced the lethality of the crude preparation by about 50%, but had no effect on the lethality of the more highly purified polysaccharide; it had no demonstrable effect, moreover, on the tumor-necrotizing activity of either preparation. Similar results were obtained with mice rendered tolerant by two injections of polysaccharide in saline. The factor in serum responsible for the decrease in toxicity of the crude preparation was stable to heating at 56°C for 30 minutes, but was inactivated by heating to 70°C for 8 minutes. Tumor implants exhibited apparent refractoriness to the tumor-necrotizing action of the polysaccharide preparations after 6 days growth in hosts rendered tolerant to the lethal action of the material before tumor implantation.

Endotoxin Inactivating Activity of Rat Serum

“…False negative test results, were they to occur, however, might also possibly result from the activity of an endotoxin inactivator in plasma or serum (LPSI or lipopolysaccharide inactivator). Such activity has indeed been shown to exist by several investigators (26,(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42). Since these studies have provided conflicting results and because no data concerning any concrete quantitative aspects of this phenomenon have so far been presented, this subject was reevaluated.…”

“…Irreversible inhibitors or hurnoral detoxifying mechanisms in blood have also been described (29-3 1) which reduce endotoxin lethality, tumor necrotizing properties, and the Shwarzman reaction. Furthermore, the results of several studies indicate that serum can alter the antigenic characteristics of endotoxins (32)(33)(34). A number of studies have characterized the active factor.…”

Inactivation of Endotoxin by a Humoral Component. Vii. Enzymatic Degradation of Endotoxin by Blood Plasma*

“…On the other hand, investigators who employed reaction mixtures which contained high concentrations of endotoxin, or mixtures that were incubated for prolonged periods at 370 C, usually observed a reduction in the pyrogenic and other toxic properties of endotoxin (8,10,(14)(15)(16)(17)(18). In much of the earlier work, however, insufficient attention was given to the critical importance of the relative concentrations of the reactants.…”

“…Other investigators working on different facets of the problem have made it evident that reaction of serum and endotoxin under appropriate conditions results in the inactivation of every hostreactive property of endotoxin thus far examined (13)(14)(15)(16)(17)(18)(19)(20) as well as in striking alterations in the immunochemical properties of the lipopolysaccharide complex (7,19). However, the mechanism by which endotoxin is inactivated by plasma has remained uncertain.…”