Lymphoid system

ACTH adrenocorticotropic hormone GALT gut-associated lymphoid system... 

Krajnc El, Wester PW, Loeber JG, et al. 1984. Toxicity of bis(tri-n-butyltin)oxide in the rat. I. Short-term effects on general parameters and on the endocrine and lymphoid systems. Toxicol Appl Pharmacol 75 363-386. 

The toxicity of antimetabolites is, as expected, due to their incorporation into the metabolism of normal cells, which is nearly identical to that of the malignant cells that they were designed to injure. The normal cells injured most severely are the rapidly proliferating cells of the bone marrow, the lymphoid system, and the GI epithelium. Thus, the common toxicities are bone marrow depression, nausea and vomiting, diarrhea, and mucositis. Cytarabine and pentostatin can cause conjunctivitis. Capecitabine and prolonged use of fluorouracil or cytarabine can cause cerebellar ataxia and the hand-foot syndrome, that is, palmar-plantar erythrodysesthesia or acral erythema. Pentostatin and high-dose methotrexate can cause renal toxicity. 

DAAB is a respiratory tract, skin, and eye irritant. DAAB yields benzene and aniline as metabolites. The proposed metabolic pathway for DAAB is that it is cleaved reductively by liver enzymes or gut flora to form aniline, benzene, and nitrogen. DAAB metabolism also results in the formation of a reactive phenyl radical, which could account for an additional risk of toxicity or carcinogenicity. The erythrocyte and lymphoid systems are major targets of DAAB toxicity. Induction of lymphoid atrophy of the thymus and other lymphoid tissues were observed, as well as methemoglobin formation, accompanying anemia, increased spleen weights, and regenerative hematopoiesis. 

The hydrocarbons (all of the above except 2-butoxyethanol) are all neurotoxicJ2°l 2-Butoxyethanol targets the respiratory system, liver, kidneys, lymphoid system, and bloodJ13 Some studies have reported that new carpet VOC emissions are sufficiently low to not adversely affect indoor air quality nor impact the human respiratory system or CNSJ20,24 Other studies, however, have reported that human exposures to new carpet emissions at very low concentrations of both the individual chemicals and total VOCs do induce serious respiratory and CNS effectsJ25,2 The diametrically opposite conclusions reached by the two sets of studies can be attributed to... 

To distinguish diffusible from bound antigens, cryostat sections are often preferred. Pre-fixation diffusion artefacts (e.g., passive uptake of non-specific antigens by cells, particularly of the lymphoid system Mason et al., 1980), which occur quite often, may be revealed by double EIH staining (e.g., k and X chains should normally not be present in the same cell) and counteracted by rapid fixation or removal of diffusible antigens by washing with cold saline. Postfixation diffusion artefacts are also frequently noticeable, e.g. after ethanol fixation (Brandtzaeg, 1982). 

In cases where Fc receptors in the tissue are a problem (cells of the lymphoid system, central nervous system and some epithelia) the use of Fab may offer a solution. Pretreatment of the samples with 2% normal serum may also obviate this problem. 

The lymphoid system, because of its rapidly proliferating tissues, is susceptible to PAH-induced toxicity. The mechanism of action for this effect is most likely inhibition of DNA synthesis. No adverse effects on this system associated with PAH exposure have been reported in humans, but several accounts of lymphoid toxicity in animals are available. A single intraperitoneal injection of benzo[a]pyrene to mice resulted in a small spleen with marked cellular depletion, prominent and edematous trabeculae, and large lymphocytes. These lesions resulted in death (Shubik and Porta 1957). The Shubik and Porta (1957) study was severely limited by the following the benzo[a]pyrene was only partly in solution, only one dose was employed, there was a small size, the purity of benzo[a]pyrene was not specified, only one sex was tested, and the presence of benzo[a]pyrene in the peritoneal cavity indicates inadequate absorption. No other similar studies were found in the literature. 

Even though these effects have not been noted in humans, and the data in animals are contained in only one study, the rapidly proliferating nature of this tissue suggest that humans exposed to PAHs may be a risk for the development of adverse effects on the lymphoid system. 

Patients with NHL present with a wide variety of symptoms, depending on the site of involvement and whether tumor involvement is nodal or extranodal. Sites of involvement and dissemination of the malignant cells can sometimes be predicted based on the cell of origin and the fact that the tumor frequently disseminates to areas where the normal counterparts of the lymphoma cells are located. Lor example, B-cell lymphomas involve areas of the lymphoid system normally populated by B-lymphocytes, such as lymph nodes, spleen, and bone marrow. T-cell lymphomas commonly disseminate to various extra-nodal sites such as the skin and lungs. In contrast to Hodgkin s lymphoma, the bone marrow is commonly involved in NHL. 

The frequency of impaired immunocompetence and increased incidence of infection in malnourished patients suggests that certain immune function tests can be used as nutrition status markers. Nutrition affects immune stams either directly, affecting primarily the lymphoid system, or indirectly by affecting cellular metabolism or organ systems that are involved with immune system regulation. Immune fimction tests used in nutrition assessment are the total lymphocyte count (TLC) and DCH reactions. Both tests are simple, readily available, and inexpensive. TLC reflects the number of... 

The lymphoid system of the amphibians is more complex than that of fishes. In addition to a well-defined thymus gland, primitive lymph node tissue is also present (Kent et al., 1964). In frogs and toads for the first time marked seasonal changes in thymic size are noted (Dustin, 1911). Reptiles have a lymphoid system that is quite similar to that seen in amphibians, including a well-developed thymus that also involutes with age (Dustin, 1911). 

The evolutionary development of the lymphoid system in birds is unique. In addition to the presence of discrete lobulated thymic tissue, there is a second discrete lymphoid organ found near the cloaca, the bursa of Fabri-cius, which functions to direct specifically the maturation of B cells and the capacity to produce humoral antibody (Glick, 1964). In contrast, the role of... 

The Best Practice Guideline also reinforced the principle that histopathologic examination of lymphoid tissues as indicators of systemic immunoto-xicity requires that (i) each animal should receive a thorough macroscopic examination of the spleen, thymus, and lymph nodes and (ii) thymus, spleen, draining lymph nodes, bone marrow in situ, and any gross lesions of a lymphoid organ represent the minimum of tissues for routine evaluation of the lymphoid system. 

The information provided above is designed to simplify and demysticize the characterization of lymphoid system lesions. It is accurate to say that standard pathology practices, applied throughout the entire drug development process, have been very successful at identifying potential immunotoxicants. But as we... 

Roughly 30 Bcl-2 family members are currently known. These proteins play tissue-specific as well as signal pathway-specific roles in regulating apoptosis. The tissue-specificity is overlapping. For example, Bcl-2 is expressed in hair follicles, kidney, small intestines, neurons, and the lymphoid system, whereas Bcl-x is expressed in the nervous system and hematopoietic cells. 

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