Lymphoid

Lymphoid cells Lymphomas Lymphosarcoma Lyochrome Lyophilization... 

One component of the age-ielated decline in immune function is decreased production of the lymphokine that promotes the growth of T-ceUs, interleukin 2 (IL-2). Administration of recombinant-derived IL-2, both in vitro and in vivo, appears to restore certain immune functions in aged mice. Recovery of T-regulatory effects on B-ceU differentiation has been reported in human cells from elderly patients treated with IL-1 and/or IL-2 (42). Similar effects have been observed in the presence of the pentapeptide thymopentin [69558-55-0] (Arg Lys Asp Val Tyr), a weU-known IL-2 inducer. Recombinant IL-2 adrninistered to aged mice for three weeks has been shown to correct the T-ceU functional deficiency associated with antigen-specific immunoglobulin production by certain lymphoid tissue (43). 

Mammalian Cells Unlike microbial cells, mammalian cells do not continue to reproduce forever. Cancerous cells have lost this natural timing that leads to death after a few dozen generations and continue to multiply indefinitely. Hybridoma cells from the fusion of two mammalian lymphoid cells, one cancerous and the other normal, are important for mammalian cell culture. They produce monoclonal antibodies for research, for affinity methods for biological separations, and for analyses used in the diagnosis and treatment of some diseases. However, the frequency of fusion is low. If the unfused cells are not killed, the myelomas 1 overgrow the hybrid cells. The myelomas can be isolated when there is a defect in their production of enzymes involved in nucleotide synthesis. Mammahan cells can produce the necessary enzymes and thus so can the fused cells. When the cells are placed in a medium in which the enzymes are necessaiy for survival, the myelomas will not survive. The unfused normal cells will die because of their limited life span. Thus, after a period of time, the hybridomas will be the only cells left ahve. 

British investigators (Haddow and Timmis 1951) synthesized and studied esters of the methanesulfonic acid. The most active derivative was the dimethylsulfonic ester of 1,4-butanedione, known as busulfan. Busulfan interacts with the thiol groups of proteins and amino acids some of its metabolites can alkylate the thiols of cysteine, peptides and proteins. Busulfan exerts selective cytotoxic activity in hematopoietic bone marrow cells and inhibits the formation of granulocytes and platelets. It slightly affects the lymphoid tissue. 

Cladribine (2-Chlordeoxyadenosine) is a synthetic purine nucleoside that is converted to an active cytotoxic metabolite by the deoxycytidine kinase. The drug is relatively selective for both normal and malignant lymphoid cells. 

Cladribine is highly active against hairy cell leukemia (complete remssions were achieved in more than 60% of patients receiving a single 7-day course). Activity has been recorded in other low-grade lymphoid malignancies. The major side effect is myelosuppression. 

Dendritic cells (DC) are important antigen-presenting cells mostly derived from the bone marrow. Microscopically they show characteristic long cytoplasmic extensions called dendrites. There are several types of specialized DC present in all lymphoid tissues and major... 

In the specialized environment of secondary lymphoid tissues such as lymph nodes or spleen, dendritic cells provide the requirements for naive T-lymphocytes to become activated and to proliferate. The professional antigen-presenting cells present peptides in MHC II, express costimulatory molecules, and release cytokines into the immunological synapse, which is formed by the antigen-presenting cell and the naive T-lymphocyte. Thus, cells of innate immunity initiate and facilitate the activation of naive lymphocytes, and it is easily conceivable that their cytokines and adhesion molecules will instruct the naive T-lymphocyte during activation and differentiation to T-effector cells. 

This experimental drug is a derivative of myriocin. After phosphorylation FTY720 modulates chemotactic responses and lymphocyte trafficking, leading to reversible lymphocyte sequestration in secondary lymphoid tissues. It is in clinical trials for the treatment of multiple sclerosis. 

S1P4 Lymphoid and haematopoietic tissue Gj/o. G12/13 Proliferation and cytokine secretion in T-cells J,... 

NF-kB is also crucial for the proper functioning of the adaptive immune system not only by acting on the immune cells themselves but also by participating in the development and organization of the secondary lymphoid organs (lymph nodes, spleen, and Peyer s patches), in which both B and T lymphocytes undergo maturation and activation. NF-kB proteins have an important role in lymphocyte development and... 

Tissue-Specific Expression. In the adult rodent, PPARy is expressed in brown and white adipose tissue, and at lower levels in intestine, retina, skeletal muscle, and lymphoid organs. In human, PPARy is most abundantly expressed in white adipose tissue and at lower levels in skeletal muscle, the heart, and liver, but not in lymphoid tissues, although PPARy has been identified in macrophages in human atheromas. 

The thymus is a lympho-epithelial organ, located within the upper thorax. One of its fimctions is the conversion of certain lymphoid hematopoietic precursor cells originating from the bone marrow into thymus-derived lymphocytes (T-cells). 

When animal cells are removed from the body, the cells can be maintained (or cultured) for prolonged periods, provided the cells are in an appropriate alternative environment. Environmental factors of importance for animal cell culture include the culture medium, substratum (or surface of the culture vessel), and temperature. The substratum (or surface) is a significant factor for those animal cells which grow attached to the surface of the culture container. A number of types of animal cells (such as lymphoid cells) grow in suspension. 

Similar studies on dimethyltin dichloride and monooctyltin trichloride showed no effects on the lymphoid organs (Seinen et al., 1977a). 

I. Atrophy of thymus and thymus-dependent lymphoid tissue in rats fed di-rr-octyltindichloride. Toxicology and Applied Pharmacology, 35(1) 63-75. 

Chinese hamster ovary Chinese hamster V79 Human lymphoid cells/LAZ-007 Human lymphocytes... 

Results of methyl parathion assays involving effects on chromosomes have also been contradictory. For sister chromatid exchange, Waters et al. (1982) reported a positive response in Chinese hamster ovary cells only in the presence of metabolic activation system, while methyl parathion tested positive without a metabolic activation system in Chinese hamster V79 cells (Chen et al. 1981), cultured normal human lymphoid cells (Chen et al. 1981 Gomez-Arroyo et al. 1987 Sobti et al. 1982), and Burkitt s l5miphoma cells (Chen et al. 1981). Chen et al. (1981) found a significant dose-related increase in sister chromatid exchange in both hamster and human cultured cells, but dose-related cell cycle delays were less pronounced in human cell lines than in V79 cells. Negative results were obtained for chromosomal aberrations in human lymphocytes without a metabolic activation system (Kumar et al. 1993). 

Sobti RC, Krishan A, Pfaffenberger CD. 1982. Cytokinetic and cytogenetic effects of some agricultural chemicals on humans lymphoid cells in vitro Organophosphates. Mutat Res 102 89-102. 

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