Null cells

Anaplastic large-cell lymphoma, T or null cell, primary cutaneous type... 

E. Diffuse, small cleaved cell 75% B cell, 20%T cell, 5% null cell... 

Immunologic phenotype Early pre-B cell Null cell,T cell, pre-B cell, B cell... 

Null cells are also known as large granular lymphocytes , but are best known as natural killer (NK) cells. These represent a third lymphocyte subgroup. They are capable of directly lysing cancer cells and virally infected cells. 

The ability of 3-phosphoinositides to stimulate cell proliferation/survival via activation of Akt is countered by the 3-phosphatase PTEN, which hydrolyzes PI(3,4)P2 and PI(3,4,5)P3. A link between PTEN activity and 3-phosphoinositide content in cells is evident from the observations that (a) overexpression of PTEN results in a dramatic reduction in the cellular content of these lipids, and (b) 3-phosphoinositide concentrations are greatly elevated in mammalian PTEN-null cell lines [28]. Cells in which PTEN activity is reduced have increased tumori-genic properties, since Akt inhibits apoptosis and promotes cell survival. Conversely, PTEN activity programs the fate of the cell toward apoptosis. Mutations of PTEN have been shown to occur in a wide range of tumor types, but with a particularly high frequency in glioblastomas. 

Null cells Antihody-dependent cell-mediated cytotoxicity (ADCC) involving non-T/non-B cells (null cells) with Fc receptors specific for antihody-coated target cells. 

Lymphocytes White blood cells formed in the body s lymphoid tissue. The nucleus is round or ovoid with coarse, irregularly clumped chromatin while the cytoplasm is typically pale blue with azurophilic (if any) granules. Most lymphocytes can be classified as either T or B (with subpopulations of each) those with characteristics of neither major class are called null cells. [NIH]... 

In vitro studies with unmodified and modified N-terminal peptides of H3 demonstrated that Lys-14 acetylation did not interfere with methylation at Lys-9 by Suv39hl, while phosphorylation at Ser-10 and acetylation at Lys-9 did (Fig. 7). Further dimethylation of Lys-9 reduced enzymatic activity [186], A Suv39h double null primary mouse embryonic fibroblasts had higher levels of Ser-10 phos-phorylated H3 than wild type cells. These mutant cells had increased numbers of micro- and polynuclei. Oversized nuclei were characteristic of subpopulation of cells. The level of Lys-9 methylated FI3 in wild type cells and Suv39h double null cells was similar, demonstrating that other FI3 methyltransferases were involved [195]. Phosphorylation of Ser-10 by Ipll/aurora was also studied. Acetylation at Lys-14 promoted the activity of the mitotic kinase, while dimethylation, but not acetylation at Lys-9, reduced activity of the kinase [186]. 

Kondo Y, Woo ES, Michalska AE, Choo AKH, Lazo JS (1995b) Metallothionein null cells have increased sensitivity to anticancer drugs. Cancer Res 55 2021-2023... 

Lymphocytes are responsible for the specificity of the immune response. They are the only immune cells that recognize and respond to specific antigens, due to the presence on their surface of high-affinity receptors. In addition to blood, lymphocytes are present in high numbers in the spleen and thymus. They may be sub-categorized into antibody-producing B lymphocytes, T lymphocytes, which are involved in cell-mediated immunity, and null cells. 

F13. Foss, H. D., Anagnostopoulos, I., Araujo, I., Assaf, C., Demel, G., Kummer, J. A., Hummel, M., and Stein, H., Anaplastic large-cell lymphomas of T-cell and null-cell phenotype express cytotoxic molecules. Blood 88, 4005-4011 (1966). 

K29. Krenacs, L., Wellmann, A., Sorbara, L., Himmelmann, A. W., Bagdi, E., Jaffe, E. S., and Raffeld, M., Cytotoxic cell antigen expression in anaplastic large cell lymphomas of T- and null-cell type and Hodgkin s disease Evidence for distinct cellular origin. Blood 89, 980-989 (1997). 

Also known as killer cells, killer T-cells, null cells. A differentiated T-ceU (CD8 positive) that attacks and lyses target cells bearing specific antigens. Used in patient-specific immunotherapy with cells grown in culture. See Gillis, S., Baker, RE., Ruscetti, F.W., and Smith, K.A., Long-term culture of human antigen-specific cytotoxic T-cell lines, J. Exptl. Med. 148, 1093-1098, 1978. 

Null cells are a separate subset of lymphocytes that lack surface markers of B or T origin. These cells, also referred to as large granular lymphocytes, are thought to perform functions such as direct cytotoxicity to foreign entities, and they act either alone (natural killer cells) or in concert with immunoglobulin (antibody-dependent cellular cytotoxicity). (Further details regarding lymphocytes are found in Chap. 84, on the immune system.)... 

B-cell origin. In contrast, BSAP is not expressed in normal or malignant T cells, and thus is absent in T/null cell ALCLs. ... 

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