APCs then present the fragments to T helper cells ( CD4 < sup >+</ sup >) by the use of class II histocompatibility molecules on their surface.

Some T cells are specific for the peptide: MHC complex.

Cytokines are substances that can activate cytotoxic T lymphocytes ( CTL ), antibody-secreting B cells, macrophages, and other particles.

If activated cytotoxic CD8 < sup >+</ sup > T cells recognize them, the T cells begin to secrete various toxins that cause the lysis or apoptosis of the infected cell.

In order to keep the cytotoxic cells from killing cells just for presenting self-proteins, self-reactive T cells are deleted from the repertoire as a result of tolerance ( also known as negative selection ).

Cytotoxic T lymphocytes that recognize these antigens may be able to destroy the tumor cells before they proliferate or metastasize.

However, with the use of cre-lox technology, a caspase 8 knock-out has been created that exhibits an increase in peripheral T cells, an impaired T cell response, and a defect in neural tube closure.

# Released viral particles and proteins present in extracellular fluid are able to induce apoptosis in nearby " bystander " T helper cells.

* Expression of viral proteins coupled to MHC proteins on the surface of the infected cell, allowing recognition by cells of the immune system ( such as Natural Killer and cytotoxic T cells ) that then induce the infected cell to undergo apoptosis.

Screening of donated blood, blood components, and solid organ donors, as well as donors of cells, tissues, and cell and tissue products for T. cruzi is mandated in all Chagas-endemic countries and has been implemented.

Although migration of cells was detected from the early days of the development of microscopy ( Leeuwenhoek ), erudite description of chemotaxis was first made by T W. Engelmann ( 1881 ) and W. F.

Scientists at the National Institutes of Health ( Bethesda, Maryland ) have successfully treated metastatic melanoma in two patients using killer T cells genetically retargeted to attack the cancer cells.

In the Phase I trial enrolling five subjects with chronic HIV infection who had failed to respond to at least two antiretroviral regimens, a single intravenous infusion of autologous CD4 T cells genetically modified with VRX496 was safe and well tolerated.

The study carried out by the researchers at the University of Pennsylvania used genetically modified T cells to fight the disease.

This has occurred in clinical trials for X-linked severe combined immunodeficiency ( X-SCID ) patients, in which hematopoietic stem cells were transduced with a corrective transgene using a retrovirus, and this led to the development of T cell leukemia in 3 of 20 patients.

It shows that in any consistent effective theory T containing PA, the formula C < sub > T </ sub > expressing the consistency of T cannot be proven within T.

* In the film Lawrence of Arabia ( 1962 ) T. E. Lawrence, played by actor Peter O ' Toole, quotes Themistocles saying, " I cannot fiddle, but I can make a great state from a little city.

But the " T " piece cannot be oriented to fill just that one remaining corner ; orienting it such that it fills zero corners will obviously not make a cube, and orienting it such that it fills two corners will not make a cube.

While killed vaccines do not have this risk, they cannot generate specific killer T cell responses, and may not work at all for some diseases.

However, s < sub > 0 </ sub > does not appear anywhere in S. Hence, T cannot coincide with S.

Because this argument applies to any countable set S of sequences of 0s and 1s, it follows that T cannot be equal to any such set.

Thus T is uncountable: it cannot be placed in one-to-one correspondence with the set of natural numbers.

As described above, any completely regular space is regular, and any T < sub > 0 </ sub > space that is not Hausdorff ( and hence not preregular ) cannot be regular.

For each consistent formal theory T having the required small amount of number theory, the corresponding Gödel sentence G asserts: " G cannot be proved within the theory T ".

This means that if the theory T is consistent then G cannot be proved within it, and so the theory T is incomplete.

This will not result in a complete theory, because Gödel's theorem will also apply to T ’, and thus T ’ cannot be complete.

New words cannot be mere plurals of existing words ; rules typically require that the new word change the root of the old, thus allowing APPEAR to become PARAPET ( APPEAR + T ), but not APPEARED (+ ED ) or REAPPEAR (+ ER ).

It is associated with the following components: 白, 手, 扌, 斤 ( both with and without the T ), 牛 ( without the vertical downward stroke ), and of course the two left-falling strokes ( I cannot find the unicode glyph that represents them ) that one would expect from the second key in the zone ( see above for an explanation ).

: If S is built up of several copies of the string T, and T cannot itself be broken down further into repeating strings, then the number of friends of S ( including S itself ) is equal to the length of T.

Structural studies have supported the MWC model and elucidated the R and T states ; however, the model cannot explain negative cooperativity.

# If it is now-necessary that T, then God cannot do otherwise.

Both postulate that enzyme subunits exist in one of two conformations, tensed ( T ) or relaxed ( R ), and that relaxed subunits bind substrate more readily than those in the tense state.

In summary, β-selection is the first checkpoint, where the T cells which are able to form a functional TCRβ chain and bind to pre-Tα are allowed to proceed.

Negative selection then removes T cells that bind too strongly to self antigens.

# positive selection, in which those double-positive T cells that bind too weakly to MHC-presented self antigens undergo apoptosis because of their inability to recognize MHC-protein complexes.

# negative selection, in which those double-positive T cells that bind too strongly to MHC-presented self antigens undergo apoptosis because they could otherwise become autoreactive, leading to autoimmunity.

Only those T cells that bind to the MHC-self-antigen complexes weakly are positively selected.

Some APCs also bind native ( or unprocessed ) antigens to their surface, such as follicular dendritic cells, but unprocessed antigens do not interact with T cells and are not involved in their activation.

Activated T cells also produce the alpha sub-unit of the IL-2 receptor ( CD25 or IL-2R ), enabling a fully functional receptor that can bind with IL-2, which in turn activates the T cell's proliferation pathways.

The autocrine or paracrine secretion of IL-2 can bind that same T < sub > h </ sub > cell or neighboring T < sub > h </ sub >' s via the IL-2R thus driving proliferation and clonal expansion.

* immune receptors that bind carbohydrates: CD1, T cell receptor, and anti-carbohydrate antibodies

Although the focus for phototransduction is on T < sub > α </ sub >, T < sub > βγ </ sub > is crucial for rhodopsin to bind to transducin.

The GTPase activity of T < sub > α </ sub > hydrolyzes GTP to GDP and changes the conformation of the T < sub > α </ sub > subunit, increasing its affinity to bind to the α and β subunits on the PDE.

Similarly, inhibitors such as ATP and PEP bind to the same allosteric site and facilitate the formation of the T state, thereby inhibiting enzyme activity.

These saturate the receptors and prevent T cells from replication and also from activating the B cells, which are responsible for the production of antibodies, which would bind to the transplanted organ and stimulate an immune response against the transplant.

The pathogenesis is that the antibodies bind to the T cell receptor, activating the T cells before they are destroyed.

However, if there are nearby T helper cells, the gp41 HIV receptors displayed on the surface of the T helper cell will bind to other similar lymphocytes.

These T cells bind to the MHC II / antigen molecule and cause activation of the B cell.

This mechanism stimulates cytokine expression and release in antigen presenting cells as well as inducing the production of costimulatory molecules that allow the cell to bind to and activate T cells more effectively.