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Soluble extracts of rat lymphoid cells were characterized in order to determine the physical relationship between the major histocompatibility (Ag-B) antigen and species or xenoantigen. Antigenic determinants recognized by rabbit anti-rat antiserum were separated from those recognized by alloantiserum by polyacrylamide gel electrophoresis (PAGE) and selective immunoabsorption. Thus, this species antigen and major H antigen are present as separate molecules on the membrane of rat lymphoid cells. [ABSTRACT FROM AUTHOR]

DeWitt, Charles W. (The Upjohn Co., Kalamazoo, Mich.) and Elizabeth A. Zell. Sialic acids (N,7-O-diacetylneuraminic acid and N-acetylneuraminic acid) in Escherichia coli. II. Their presence on the cell wall surface and relationship to K antigen. J. Bacteriol. 82:849-856. 1961.-Sialic acids obtained from Escherichia coli by weak acid hydrolysis are shown to be released from the extreme-surface, lipoprotein layer of the cell. Hydrolysis does not lyse the cells nor release cell walls. Hydrolysates do not contain compounds such as alpha, epsilon-diaminopimelic acid or N-acetylmuramic acid, normally associated with cell walls. The surface material is released in a relatively homogeneous form by simple incubation of live cells in an acidic buffer and is susceptible to hydrolysis by viral neuraminidase, although untreated live cells will not serve as substrate. As this surface material resembles, in its initial rate of reaction with neuraminidase, human urinary mucoprotein, the sialic acid is presumably present as an alpha-ketoside. Colominic acid is insusceptible under the same conditions. Although there is good correlation of the occurrence of sialic acids with the E. coli capsular antigen, K(1), specific release of sialic acid from K(1) antigen with neuraminidase does not lessen its haptenic activity as measured by inhibition of specific agglutination.

Bolaños, Roger (Tulane University, New Orleans, La.), and Charles W. DeWitt. Isolation and characterization of the K1 (L) antigen of Escherichia coli. J. Bacteriol. 91:987-996. 1966.-An acidic polysaccharide with the serological properties of the K1 (L) antigen has been isolated from Escherichia coli O2:K1:H4 by means of phenol-water extraction, fractionation with hexadecyltrimethylammonium bromide (Cetavlon), filtration through Sephadex G-200, and chromatography on anion-exchange cellulose columns. Nucleic acid and protein content were reduced to a nondetectable level. There is no contamination with O antigen. The active material appears in two different positions in the Cetavlon fractionation, each with a slightly different serological specificity, as followed by the inhibition of passive hemagglutination. By paper chromatography, the polysaccharide moiety of the O antigenic fraction is composed of glucose, galactose, hexosamine and rhamnose. The absence of colanic acid in either K1 fraction was not proven, although its participation in our assay system, as well as the participation of the common or cross-reacting antigen, was ruled out by serological means.

The mouse virulence of two K antigen-containing (L variety) strains of Escherichia coli (serotype O2:K1) isolated from human septicemia, and of their variants which lacked K antigen, was studied. The strains containing envelope antigen (K+) were highly virulent when injected intracerebrally or when suspended in mucin and injected intraperitoneally. After intraperitoneal injection of E-107 K+ (but not K-), there was a marked initial growth in the peritoneal cavity followed by bacteremia and infection of all the organs examined. In the mucin-enhanced lethal infection, this growth continued until death of the animal; in the nonlethal infection, growth ceased and the count dropped quickly after approximately 5 hr. Host defenses were depressed greatly by intraperitoneally, but not intravenously, administered mucin. Bacteria were most virulent when injected intraperitoneally. In vitro phagocytosis of the K+ bacteria required opsonins not needed for phagocytosis of the smooth K- variants. Opsonins were found in immunized rabbit and normal mouse sera. Immune rabbit sera contained antibodies with anti-K specificity which were opsonic in vitro and highly protective in vivo when administered passively. There appears to be a lesser anti-O opsonic and protective activity involving one of the strains (E-107 K+), and colonial morphology, agglutination, and absorption tests indicated a low amount of K antigen on this organism. No anti-O opsonic or protective activity could be shown involving the other strain (E-102 K+). When standard serological typing procedures were used, these two strains appeared to be identical serologically, but they differed greatly in sensitivity to immune rabbit serum in phagocytosis experiments in vitro.

DeWitt, Charles W. (The Upjohn Co., Kalamazoo, Mich.) and Janet A. Rowe. Sialic acids (N,7-O-diacetylneuraminic acid and N-acetylneuraminic acid) in Escherichia coli. I. Isolation and identification. J. Bacteriol. 82:838-848. 1961.-Two sialic acids, N-acetylneuraminic acid and N,7-O-diacetylneuraminic acid, were obtained in crude mixtures from whole cells of Escherichia coli and from its endotoxin by weak acid hydrolysis followed by anion exchange resin chromatography. Yields from whole cells were 0.1 to 0.2% (dry weight) with 50 to 60% purity. Identification of the sialic acids was by comparative paper chromatography and colorimetric assays using the acidic p-dimethylaminobenzaldehyde (direct Ehrlich), resorcinol and thiobarbituric acid reactions. The N-acetyl derivative was also shown to be susceptible to hydrolysis by clostridial N-acetylneuraminic aldolase and the end products identified, N-acetylamannosamine by paper chromatography and pyruvic acid by oxidation of DPNH with lactic acid dehydrogenase. The two sialic acids were separated on paper chromatograms, eluted, and assays for total and ester acyl groups showed the suspected N-acetyl derivative to contain 0.11 O-acyl and 1.16 N-acetyl groups per mole sialic acid and the diacetyl derivative to have 1.10 O-acyl and 0.93 N-acetyl groups per mole. The O-acyl group was identified as acetyl by preparation of the hydroxamate.