Salmonella Typhi survives in the host by evading a complement-dependent neutrophil immuno-surveillance (P4221)

Vi capsular polysaccharide in S. Typhi is an important virulence factor. However, its role is incompletely understood. Previously, we have shown that the Vi capsule prevents complement component 3 mediated clearance of S. Typhi by preventing C3 fixation on the bacterial surface. Here we used isolated mouse and human neutrophils to show, at single cell level, that Vi negative S. Typhi mutant (tviB-vexE) directly triggers a chemotactic response by neutrophils when co-incubated in a medium containing autologous serum whereas Vi positive wild-type S. Typhi (Ty2) does not. Using neutrophils from C3 and C5aR deficient mice, we also show that this chemotactic response requires the complement component 5a receptor (C5aR) in neutrophils suggesting that the detection of generated C5a as a result of complement activation on the bacterial surface is a non-redundant signal used by neutrophils to move towards the bacteria. Additionally, data from our in vivo mouse model show that higher number neutrophils were associated with tviB-vexE than the WT S. Typhi an hour post interperitoneal injection of bacteria. Taken together, our data suggest that Vi capsule helps evade neutrophil detection of S. Typhi by preventing activation of C5a-dependent chemotactic response.

Ligandin content of normal and carcinogen-treated rat tissues

Ligandin was detected by immunofluorescence in tissue sections and determined by immunoquantitation in the cytosols of the liver, kidney and testes of normal and carcinogen-treated rats. Ligandin was not detected by either of these procedures in normal or carcinogen-treated rat lung, spleen, brain, and skeletal or cardiac muscle.

Detection by antihapten antibodies of liver-bound compounds related to azocarcinogens or their metabolites

The localization of known azocarcinogens and metabolites such as p-aminoazobenzene and N-methyl-p-aminoazobenzene bound to components of liver cells of rats fed single or multiple doses of 3'-methyl-p-dimethylaminoazobenzene has been determined with the use of antibodies raised against p'-azo-p-aminoazobenzene and p'-azo-N-monomethyl-p-aminoazobenzene in the indirect fluorescent antibody procedure. These 2 antisera reacted with liver cells of rats fed 3'-methyl-p-dimethylaminoazobenzene, p'-amino-p-aminoazobenzene, p'-amino-N-monomethyl-p-aminoazobenzene and N-methyl-p-aminoazobenzene. The results obtained in this study suggest that both major and minor metabolites of azocarcinogens have common antigenic determinants.

Distribution of ligandin in normal and azocarcinogen-treated rat liver and azocarcinogen-induced liver tumors

Antibodies were raised in rabbits against pure ligandin. Employing the fluorescent antibody procedure, an antigen identical to ligandin was shown to be uniformly distributed in the hepatic cells of both normal rat liver and in early and late 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB)-treated liver. Ligandin was absent in liver carcinomas induced by this azocarcinogen. The results obtained with fluorescent antibody procedure were confirmed by the immunoquantitation of ligandin in the cytosols prepared from normal rat liver, early and late 3'-Me-DAB-treated liver, mixtures of both late 3'-Me-DAB-treated liver and liver carcinomas and liver carcinomas. Riboflavin-deficient diets lowered significantly the hepatic ligandin content.

Hepatoma induction in the rat by the subcutaneous administration of powdered 3'-methyl-p-dimethylaminoazobenzene

A relatively safe and simple procedure was developed for the induction of hepatomas in the rat by the s.c. administration of powdered 3'-methyl-p-dimethylaminoazobenzene.

A distinctive antigen present in liver carcinomas induced by 3'-methyl-p-dimethylaminoazobenzene

Hepatocellular carcinomas and cholangiocarcinomas induced in rat liver by the administration of 3'-methyl-p-dimethyl-aminoazobenzene (3'-Me-DAB) were found to contain a carcinoma distinctive antigen by immunofluorescence, immunoelectrophoresis and immunodiffusion. This carcinoma distinctive antigen does not appear to be alpha-fetoprotein (AFP) or the preneoplastic antigen.

Detection of liver-bound metabolites of azocarcinogens by the use of anti-hapten antibodies

The presence of the azocompounds, p-dimethylaminoazobenzene and 3'-methyl-p-dimethylaminoazobenzene, and p-amino-N-acetyl-N-methylaniline (or their metabolites) bound to components of the liver cells of rats fed a single large dose of each compound has been detected using rabbit antibodies raised against the p-azo-N-acetyl-N-methylaniline hapten in the indirect fluorescent antibody technique. Binding of these antibodies was seen on liver sections from rats fed any one of these compounds. When the anti-p-azo-N-acetyl-N-methylaniline antiserum was absorbed with either liver sediments or cytosol fractions from rats fed p-amino-N-acetyl-N-methylaniline, the antibodies reacting with the liver-bound compounds were removed from the antiserum. Also, absorption of the antiserum with liver sediments or cytosol fractions of rats fed either one of the azocompounds selectively removed all of the antibodies reacting with the livers of rats fed that compound but did not remove other antibodies that were still capable of reacting with liver cells of rats fed the other azocompound or p-amino-N-acetyl-N-methylaniline. Thus this antiserum appears to contain several different anti-p-azo-N-acetyl-N-methylaniline antibodies with different structural requirements for reaction. Some can react with the azocompounds or certain of their metabolites, while others require more of the p-azo-N-acetyl-N-methylaniline structure for reaction. Some of the antibodies appear to react with liver-bound p-dimethylaminoazobenzene but not with liver-bound 3'-methyl-p-dimethylaminoazobenzene, while still others react with 3'-methyl-p-dimethylaminoazobenzene but not with p-dimethylaminoazobenzene.

Binding of the azocarcinogen 3'-methyl-p-dimethylaminoazobenzene to cellular components of normal rat liver and azocarcinogen-induced hepatomas

The location of binding sites for 3'-methyl-p-dimethylaminoazobenzene (3'-Me-DAB) or metabolites on components of rat liver cells and hepatoma cells in tumors induced by this carcinogen was determined at 2 stages during the induction of tumors in rats: (a) in normal liver immediately following the application of a massive dose of the azocarcinogen by intragastric feeding, and (b) in liver and tumor after hepatomas had developed following repeated exposures to the carcinogen by s.c. injections. Bound 3'-Me-DAB or metabolites were detected by the use of rabbit antisera directed against either p-azoazobenzene or p'-azo-p-dimethylaminoazobenzene in an indirect fluorescent antibody technique. Soon after massive intragastric doses of 3'-Me-DAB, the staining observed when the anti-p-azoazobenzene antiserum was used was principally on cytoplasmic components of liver cells with some staining of the intranuclear components. When the second antiserum, anti-p'-azo-p-dimethylaminoazobenzene antiserum, was used, the most intense fluorescent staining was on the nuclear membranes, although there was some cytoplasmic and intranuclear staining as well.

Immunological escape mechanism in spontaneously metastasizing mammary tumors

Immunological and biochemical studies of spontaneously metastasizing and nonmetastasizing rat mammary carcinomas and their plasma membranes indicated that: (i) all spontaneously metastasizing tumors have little or no demonstrable glycocalyx, while all nonmetastasizing tumors have a thick glycocalyx; (ii) there is a direct relationship between the glycocalyx and immunogenicity, and an inverse relationship with the metastasizing capacity of tumor cells, properties which can be quantitated by levels of the plasma membrane marker enzyme 5'-nucleotidase (EC3.1.3.5;5'-ribonucleotide phosphohydrolase) activity; (iii) the absence of glycocalyx from the metastasizing tumor cell surface seems to result from its dissociation from plasma membranes, for solubilized cell surface antigen is readily found in the blood of metastasizing tumor bearing rats, while there was no detectable tumor cell surface antigen in the blood of the nonmetastasizing tumor hosts tested; (iv) both metastasizing and nonmetastasizing mammary tumors appear to have a common soluble cell surface antigen; (v) in addition to this common antigen, there is another membrane-bound antigen in the nonmetastasizing, immunogenic tumor cell surface which presumably is the tumor specific transplantation antigen; and (vi) this antigen is immunobiologically unique, but seems to be immunochemically related to the common soluble antigen. It is postulated that the lack of an immunogenic coat and/or the presence of solubilized tumor cell surface antigen in the blood may provide an immune escape mechanism for tumor cells by interfering with cell-mediated immune response of tumor hosts, leading to their dissemination.