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Salmonella Infections: Infections with bacteria of the genus SALMONELLA.Salmonella Infections, Animal: Infections in animals with bacteria of the genus SALMONELLA.Salmonella: A genus of gram-negative, facultatively anaerobic, rod-shaped bacteria that utilizes citrate as a sole carbon source. It is pathogenic for humans, causing enteric fevers, gastroenteritis, and bacteremia. Food poisoning is the most common clinical manifestation. Organisms within this genus are separated on the basis of antigenic characteristics, sugar fermentation patterns, and bacteriophage susceptibility.Salmonella typhimurium: A serotype of Salmonella enterica that is a frequent agent of Salmonella gastroenteritis in humans. It also causes PARATYPHOID FEVER.Salmonella enterica: A subgenus of Salmonella containing several medically important serotypes. The habitat for the majority of strains is warm-blooded animals.Salmonella Food Poisoning: Poisoning caused by ingestion of food harboring species of SALMONELLA. Conditions of raising, shipping, slaughtering, and marketing of domestic animals contribute to the spread of this bacterium in the food supply.Salmonella enteritidis: A serotype of Salmonella enterica which is an etiologic agent of gastroenteritis in man and other animals.Salmonella typhi: A serotype of SALMONELLA ENTERICA which is the etiologic agent of TYPHOID FEVER.Salmonella Vaccines: Vaccines or candidate vaccines used to prevent infection with SALMONELLA. This includes vaccines used to prevent TYPHOID FEVER or PARATYPHOID FEVER; (TYPHOID-PARATYPHOID VACCINES), and vaccines used to prevent nontyphoid salmonellosis.Salmonella arizonae: Gram-negative rods widely distributed in LIZARDS and SNAKES, and implicated in enteric, bone (BONE DISEASES), and joint infections (JOINT DISEASES) in humans.Salmonella Phages: Viruses whose host is Salmonella. A frequently encountered Salmonella phage is BACTERIOPHAGE P22.Salmonella paratyphi A: A serotype of SALMONELLA ENTERICA that causes mild PARATYPHOID FEVER in humans.Food Microbiology: The presence of bacteria, viruses, and fungi in food and food products. This term is not restricted to pathogenic organisms: the presence of various non-pathogenic bacteria and fungi in cheeses and wines, for example, is included in this concept.Typhoid Fever: An acute systemic febrile infection caused by SALMONELLA TYPHI, a serotype of SALMONELLA ENTERICA.Reptiles: Cold-blooded, air-breathing VERTEBRATES belonging to the class Reptilia, usually covered with external scales or bony plates.Salmonella paratyphi B: A serotype of SALMONELLA ENTERICA which is an agent of PARATYPHOID FEVER in humans.Serotyping: Process of determining and distinguishing species of bacteria or viruses based on antigens they share.Feces: Excrement from the INTESTINES, containing unabsorbed solids, waste products, secretions, and BACTERIA of the DIGESTIVE SYSTEM.Poultry Diseases: Diseases of birds which are raised as a source of meat or eggs for human consumption and are usually found in barnyards, hatcheries, etc. The concept is differentiated from BIRD DISEASES which is for diseases of birds not considered poultry and usually found in zoos, parks, and the wild.Disease Outbreaks: Sudden increase in the incidence of a disease. The concept includes EPIDEMICS and PANDEMICS.Pipidae: A family of the order Anura, distinguished by the lack of a tongue. It includes four living genera of aquatic "toads". Two of the most familiar pipids are the popularly called Surinam "toad" (Pipa pipa) and XENOPUS LAEVIS.Swine Diseases: Diseases of domestic swine and of the wild boar of the genus Sus.Bacterial Proteins: Proteins found in any species of bacterium.Cecum: The blind sac or outpouching area of the LARGE INTESTINE that is below the entrance of the SMALL INTESTINE. It has a worm-like extension, the vermiform APPENDIX.Eggs: Animal reproductive bodies, or the contents thereof, used as food. The concept is differentiated from OVUM, the anatomic or physiologic entity.Food Contamination: The presence in food of harmful, unpalatable, or otherwise objectionable foreign substances, e.g. chemicals, microorganisms or diluents, before, during, or after processing or storage.Paratyphoid Fever: A prolonged febrile illness commonly caused by several Paratyphi serotypes of SALMONELLA ENTERICA. It is similar to TYPHOID FEVER but less severe.Carbadox: An antibacterial agent that has been used in veterinary practice for treating swine dysentery and enteritis and for promoting growth. However, its use has been prohibited in the UK following reports of carcinogenicity and mutagenicity. (From Martindale, The Extra Pharmacopoeia, 30th ed, p125)Enterocolitis: Inflammation of the MUCOSA of both the SMALL INTESTINE and the LARGE INTESTINE. Etiology includes ISCHEMIA, infections, allergic, and immune responses.Anti-Bacterial Agents: Substances that reduce the growth or reproduction of BACTERIA.Poultry: Domesticated birds raised for food. It typically includes CHICKENS; TURKEYS, DUCKS; GEESE; and others.Food Handling: Any aspect of the operations in the preparation, processing, transport, storage, packaging, wrapping, exposure for sale, service, or delivery of food.Abattoirs: Places where animals are slaughtered and dressed for market.Virulence: The degree of pathogenicity within a group or species of microorganisms or viruses as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenic capacity of an organism is determined by its VIRULENCE FACTORS.Enteritis: Inflammation of any segment of the SMALL INTESTINE.Intestines: The section of the alimentary canal from the STOMACH to the ANAL CANAL. It includes the LARGE INTESTINE and SMALL INTESTINE.Gastroenteritis: INFLAMMATION of any segment of the GASTROINTESTINAL TRACT from ESOPHAGUS to RECTUM. Causes of gastroenteritis are many including genetic, infection, HYPERSENSITIVITY, drug effects, and CANCER.Colony Count, Microbial: Enumeration by direct count of viable, isolated bacterial, archaeal, or fungal CELLS or SPORES capable of growth on solid CULTURE MEDIA. The method is used routinely by environmental microbiologists for quantifying organisms in AIR; FOOD; and WATER; by clinicians for measuring patients' microbial load; and in antimicrobial drug testing.Pets: Animals kept by humans for companionship and enjoyment, as opposed to DOMESTIC ANIMALS such as livestock or farm animals, which are kept for economic reasons.Flagellin: A protein with a molecular weight of 40,000 isolated from bacterial flagella. At appropriate pH and salt concentration, three flagellin monomers can spontaneously reaggregate to form structures which appear identical to intact flagella.Antibodies, Bacterial: Immunoglobulins produced in a response to BACTERIAL ANTIGENS.Chickens: Common name for the species Gallus gallus, the domestic fowl, in the family Phasianidae, order GALLIFORMES. It is descended from the red jungle fowl of SOUTHEAST ASIA.TurtlesMice, Inbred C57BLSpleen: An encapsulated lymphatic organ through which venous blood filters.Swine: Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).Electrophoresis, Gel, Pulsed-Field: Gel electrophoresis in which the direction of the electric field is changed periodically. This technique is similar to other electrophoretic methods normally used to separate double-stranded DNA molecules ranging in size up to tens of thousands of base-pairs. However, by alternating the electric field direction one is able to separate DNA molecules up to several million base-pairs in length.Macrophages: The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood MONOCYTES. Main types are PERITONEAL MACROPHAGES; ALVEOLAR MACROPHAGES; HISTIOCYTES; KUPFFER CELLS of the liver; and OSTEOCLASTS. They may further differentiate within chronic inflammatory lesions to EPITHELIOID CELLS or may fuse to form FOREIGN BODY GIANT CELLS or LANGHANS GIANT CELLS. (from The Dictionary of Cell Biology, Lackie and Dow, 3rd ed.)Animals, Domestic: Animals which have become adapted through breeding in captivity to a life intimately associated with humans. They include animals domesticated by humans to live and breed in a tame condition on farms or ranches for economic reasons, including LIVESTOCK (specifically CATTLE; SHEEP; HORSES; etc.), POULTRY; and those raised or kept for pleasure and companionship, e.g., PETS; or specifically DOGS; CATS; etc.Peyer's Patches: Lymphoid tissue on the mucosa of the small intestine.Mice, Inbred BALB CDNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Meat: The edible portions of any animal used for food including domestic mammals (the major ones being cattle, swine, and sheep) along with poultry, fish, shellfish, and game.Bacterial Translocation: The passage of viable bacteria from the GASTROINTESTINAL TRACT to extra-intestinal sites, such as the mesenteric lymph node complex, liver, spleen, kidney, and blood. Factors that promote bacterial translocation include overgrowth with gram-negative enteric bacilli, impaired host immune defenses, and injury to the INTESTINAL MUCOSA resulting in increased intestinal permeability. Bacterial translocation from the lung to the circulation is also possible and sometimes accompanies MECHANICAL VENTILATION.Toll-Like Receptor 5: A pattern recognition receptor that binds FLAGELLIN. It mediates cellular responses to certain bacterial pathogens.Arthritis, Reactive: An aseptic, inflammatory arthritis developing secondary to a primary extra-articular infection, most typically of the GASTROINTESTINAL TRACT or UROGENITAL SYSTEM. The initiating trigger pathogens are usually SHIGELLA; SALMONELLA; YERSINIA; CAMPYLOBACTER; or CHLAMYDIA TRACHOMATIS. Reactive arthritis is strongly associated with HLA-B27 ANTIGEN.Antigens, Bacterial: Substances elaborated by bacteria that have antigenic activity.Focal InfectionMononuclear Phagocyte System: Mononuclear cells with pronounced phagocytic ability that are distributed extensively in lymphoid and other organs. It includes MACROPHAGES and their precursors; PHAGOCYTES; KUPFFER CELLS; HISTIOCYTES; DENDRITIC CELLS; LANGERHANS CELLS; and MICROGLIA. The term mononuclear phagocyte system has replaced the former reticuloendothelial system, which also included less active phagocytic cells such as fibroblasts and endothelial cells. (From Illustrated Dictionary of Immunology, 2d ed.)Immunity, Innate: The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from the presence of naturally occurring ANTI-INFECTIVE AGENTS, constitutional factors such as BODY TEMPERATURE and immediate acting immune cells such as NATURAL KILLER CELLS.Zoonoses: Diseases of non-human animals that may be transmitted to HUMANS or may be transmitted from humans to non-human animals.Disease Susceptibility: A constitution or condition of the body which makes the tissues react in special ways to certain extrinsic stimuli and thus tends to make the individual more than usually susceptible to certain diseases.Vaccines, Attenuated: Live vaccines prepared from microorganisms which have undergone physical adaptation (e.g., by radiation or temperature conditioning) or serial passage in laboratory animal hosts or infected tissue/cell cultures, in order to produce avirulent mutant strains capable of inducing protective immunity.Bacterial Vaccines: Suspensions of attenuated or killed bacteria administered for the prevention or treatment of infectious bacterial disease.Receptors, Interleukin-12: Cell surface receptors for INTERLEUKIN-12. They exist as dimers of beta 1 and beta 2 subunits. Signaling from interleukin-12 receptors occurs through their interaction with JANUS KINASES.Drug Resistance, Multiple, Bacterial: The ability of bacteria to resist or to become tolerant to several structurally and functionally distinct drugs simultaneously. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Intestinal Diseases: Pathological processes in any segment of the INTESTINE from DUODENUM to RECTUM.Microbial Sensitivity Tests: Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).Plasmids: Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Ceftriaxone: A broad-spectrum cephalosporin antibiotic with a very long half-life and high penetrability to meninges, eyes and inner ears.Bacteriophage Typing: A technique of bacterial typing which differentiates between bacteria or strains of bacteria by their susceptibility to one or more bacteriophages.Lipopolysaccharides: Lipid-containing polysaccharides which are endotoxins and important group-specific antigens. They are often derived from the cell wall of gram-negative bacteria and induce immunoglobulin secretion. The lipopolysaccharide molecule consists of three parts: LIPID A, core polysaccharide, and O-specific chains (O ANTIGENS). When derived from Escherichia coli, lipopolysaccharides serve as polyclonal B-cell mitogens commonly used in laboratory immunology. (From Dorland, 28th ed)Genes, Bacterial: The functional hereditary units of BACTERIA.Cattle Diseases: Diseases of domestic cattle of the genus Bos. It includes diseases of cows, yaks, and zebus.Drug Resistance, Bacterial: The ability of bacteria to resist or to become tolerant to chemotherapeutic agents, antimicrobial agents, or antibiotics. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Genomic Islands: Distinct units in some bacterial, bacteriophage or plasmid GENOMES that are types of MOBILE GENETIC ELEMENTS. Encoded in them are a variety of fitness conferring genes, such as VIRULENCE FACTORS (in "pathogenicity islands or islets"), ANTIBIOTIC RESISTANCE genes, or genes required for SYMBIOSIS (in "symbiosis islands or islets"). They range in size from 10 - 500 kilobases, and their GC CONTENT and CODON usage differ from the rest of the genome. They typically contain an INTEGRASE gene, although in some cases this gene has been deleted resulting in "anchored genomic islands".Intestinal Mucosa: Lining of the INTESTINES, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. In the SMALL INTESTINE, the mucosa is characterized by a series of folds and abundance of absorptive cells (ENTEROCYTES) with MICROVILLI.Animal Feed: Foodstuff used especially for domestic and laboratory animals, or livestock.Streptomycin: An antibiotic produced by the soil actinomycete Streptomyces griseus. It acts by inhibiting the initiation and elongation processes during protein synthesis.Ciprofloxacin: A broad-spectrum antimicrobial carboxyfluoroquinoline.Caspase 1: A long pro-domain caspase that has specificity for the precursor form of INTERLEUKIN-1BETA. It plays a role in INFLAMMATION by catalytically converting the inactive forms of CYTOKINES such as interleukin-1beta to their active, secreted form. Caspase 1 is referred as interleukin-1beta converting enzyme and is frequently abbreviated ICE.Drug Resistance, Microbial: The ability of microorganisms, especially bacteria, to resist or to become tolerant to chemotherapeutic agents, antimicrobial agents, or antibiotics. This resistance may be acquired through gene mutation or foreign DNA in transmissible plasmids (R FACTORS).Gene Expression Regulation, Bacterial: Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.Bacteremia: The presence of viable bacteria circulating in the blood. Fever, chills, tachycardia, and tachypnea are common acute manifestations of bacteremia. The majority of cases are seen in already hospitalized patients, most of whom have underlying diseases or procedures which render their bloodstreams susceptible to invasion.Disease Reservoirs: Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (DISEASE VECTORS) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks.Population Surveillance: Ongoing scrutiny of a population (general population, study population, target population, etc.), generally using methods distinguished by their practicability, uniformity, and frequently their rapidity, rather than by complete accuracy.Diarrhea: An increased liquidity or decreased consistency of FECES, such as running stool. Fecal consistency is related to the ratio of water-holding capacity of insoluble solids to total water, rather than the amount of water present. Diarrhea is not hyperdefecation or increased fecal weight.Escherichia coli: A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.Salmonella paratyphi C: A serotype of SALMONELLA ENTERICA which is an agent of PARATYPHOID FEVER in Asia, Africa, and southern Europe.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.United StatesIleum: The distal and narrowest portion of the SMALL INTESTINE, between the JEJUNUM and the ILEOCECAL VALVE of the LARGE INTESTINE.Probiotics: Live microbial DIETARY SUPPLEMENTS which beneficially affect the host animal by improving its intestinal microbial balance. Antibiotics and other related compounds are not included in this definition. In humans, lactobacilli are commonly used as probiotics, either as single species or in mixed culture with other bacteria. Other genera that have been used are bifidobacteria and streptococci. (J. Nutr. 1995;125:1401-12)Anti-Infective Agents: Substances that prevent infectious agents or organisms from spreading or kill infectious agents in order to prevent the spread of infection.Immunity: Nonsusceptibility to the invasive or pathogenic effects of foreign microorganisms or to the toxic effect of antigenic substances.Cattle: Domesticated bovine animals of the genus Bos, usually kept on a farm or ranch and used for the production of meat or dairy products or for heavy labor.Carrier State: The condition of harboring an infective organism without manifesting symptoms of infection. The organism must be readily transmissible to another susceptible host.Case-Control Studies: Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.Cation Transport Proteins: Membrane proteins whose primary function is to facilitate the transport of positively charged molecules (cations) across a biological membrane.Interferon-gamma: The major interferon produced by mitogenically or antigenically stimulated LYMPHOCYTES. It is structurally different from TYPE I INTERFERON and its major activity is immunoregulation. It has been implicated in the expression of CLASS II HISTOCOMPATIBILITY ANTIGENS in cells that do not normally produce them, leading to AUTOIMMUNE DISEASES.Mice, Inbred C3HEnzyme-Linked Immunosorbent Assay: An immunoassay utilizing an antibody labeled with an enzyme marker such as horseradish peroxidase. While either the enzyme or the antibody is bound to an immunosorbent substrate, they both retain their biologic activity; the change in enzyme activity as a result of the enzyme-antibody-antigen reaction is proportional to the concentration of the antigen and can be measured spectrophotometrically or with the naked eye. Many variations of the method have been developed.Information Services: Organized services to provide information on any questions an individual might have using databases and other sources. (From Random House Unabridged Dictionary, 2d ed)Liver: A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Administration, Oral: The giving of drugs, chemicals, or other substances by mouth.Mutagenicity Tests: Tests of chemical substances and physical agents for mutagenic potential. They include microbial, insect, mammalian cell, and whole animal tests.Cytokines: Non-antibody proteins secreted by inflammatory leukocytes and some non-leukocytic cells, that act as intercellular mediators. They differ from classical hormones in that they are produced by a number of tissue or cell types rather than by specialized glands. They generally act locally in a paracrine or autocrine rather than endocrine manner.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Flagella: A whiplike motility appendage present on the surface cells. Prokaryote flagella are composed of a protein called FLAGELLIN. Bacteria can have a single flagellum, a tuft at one pole, or multiple flagella covering the entire surface. In eukaryotes, flagella are threadlike protoplasmic extensions used to propel flagellates and sperm. Flagella have the same basic structure as CILIA but are longer in proportion to the cell bearing them and present in much smaller numbers. (From King & Stansfield, A Dictionary of Genetics, 4th ed)Typhoid-Paratyphoid Vaccines: Vaccines used to prevent TYPHOID FEVER and/or PARATYPHOID FEVER which are caused by various species of SALMONELLA. Attenuated, subunit, and inactivated forms of the vaccines exist.O Antigens: The lipopolysaccharide-protein somatic antigens, usually from gram-negative bacteria, important in the serological classification of enteric bacilli. The O-specific chains determine the specificity of the O antigens of a given serotype. O antigens are the immunodominant part of the lipopolysaccharide molecule in the intact bacterial cell. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Shigella: A genus of gram-negative, facultatively anaerobic, rod-shaped bacteria that ferments sugar without gas production. Its organisms are intestinal pathogens of man and other primates and cause bacillary dysentery (DYSENTERY, BACILLARY).Culture Media: Any liquid or solid preparation made specifically for the growth, storage, or transport of microorganisms or other types of cells. The variety of media that exist allow for the culturing of specific microorganisms and cell types, such as differential media, selective media, test media, and defined media. Solid media consist of liquid media that have been solidified with an agent such as AGAR or GELATIN.Epithelial Cells: Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells.Receptors, Antigen, T-Cell, gamma-delta: T-cell receptors composed of CD3-associated gamma and delta polypeptide chains and expressed primarily in CD4-/CD8- T-cells. The receptors appear to be preferentially located in epithelial sites and probably play a role in the recognition of bacterial antigens. The T-cell receptor gamma/delta chains are separate and not related to the gamma and delta chains which are subunits of CD3 (see ANTIGENS, CD3).Macrophages, Peritoneal: Mononuclear phagocytes derived from bone marrow precursors but resident in the peritoneum.Operon: In bacteria, a group of metabolically related genes, with a common promoter, whose transcription into a single polycistronic MESSENGER RNA is under the control of an OPERATOR REGION.Bacteriological Techniques: Techniques used in studying bacteria.Seasons: Divisions of the year according to some regularly recurrent phenomena usually astronomical or climatic. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Enterobacteriaceae: A family of gram-negative, facultatively anaerobic, rod-shaped bacteria that do not form endospores. Its organisms are distributed worldwide with some being saprophytes and others being plant and animal parasites. Many species are of considerable economic importance due to their pathogenic effects on agriculture and livestock.Immunization, Passive: Transfer of immunity from immunized to non-immune host by administration of serum antibodies, or transplantation of lymphocytes (ADOPTIVE TRANSFER).Phagocytosis: The engulfing and degradation of microorganisms; other cells that are dead, dying, or pathogenic; and foreign particles by phagocytic cells (PHAGOCYTES).Vaccination: Administration of vaccines to stimulate the host's immune response. This includes any preparation intended for active immunological prophylaxis.Lymphocyte Activation: Morphologic alteration of small B LYMPHOCYTES or T LYMPHOCYTES in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific ANTIGENS. It may also occur in vivo as in GRAFT REJECTION.CD4-Positive T-Lymphocytes: A critical subpopulation of T-lymphocytes involved in the induction of most immunological functions. The HIV virus has selective tropism for the T4 cell which expresses the CD4 phenotypic marker, a receptor for HIV. In fact, the key element in the profound immunosuppression seen in HIV infection is the depletion of this subset of T-lymphocytes.Mutagens: Chemical agents that increase the rate of genetic mutation by interfering with the function of nucleic acids. A clastogen is a specific mutagen that causes breaks in chromosomes.Immunoglobulin G: The major immunoglobulin isotype class in normal human serum. There are several isotype subclasses of IgG, for example, IgG1, IgG2A, and IgG2B.Interleukin-12: A heterodimeric cytokine that plays a role in innate and adaptive immune responses. Interleukin-12 is a 70 kDa protein that is composed of covalently linked 40 kDa and 35 kDa subunits. It is produced by DENDRITIC CELLS; MACROPHAGES and a variety of other immune cells and plays a role in the stimulation of INTERFERON-GAMMA production by T-LYMPHOCYTES and NATURAL KILLER CELLS.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Colon: The segment of LARGE INTESTINE between the CECUM and the RECTUM. It includes the ASCENDING COLON; the TRANSVERSE COLON; the DESCENDING COLON; and the SIGMOID COLON.Infant, Newborn: An infant during the first month after birth.Incidence: The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from PREVALENCE, which refers to all cases, new or old, in the population at a given time.Tetrathionic Acid: A sulfuric acid dimer, formed by disulfide linkage. This compound has been used to prolong coagulation time and as an antidote in cyanide poisoning.