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What are T cells?

T cells are one of two primary types of lymphocytes, which are white blood cells found in blood and lymph tissue in the body. T cells can be recognized by the presence of the T cell receptor (TCR) located on their cell surface. Each T cell contains a single round nucleus.

Lymphocytes account for about 25% of white blood cells, and T cells represent approximately 80% of total lymphocytes.

Where do T cells originate?

T cells originate from the bone marrow, which is the soft fatty tissue inside bones.

Where do T cells mature?

T cells migrate from the bone marrow to the thymus, a small gland located in the neck. Here, they mature and differentiate into different types of T cells, such as CD8+ T cells and CD4+ T cells.

What is the function of T cells?

T cells play a central role in the body’s adaptive immune response. They recognize and destroy foreign invaders, such as virus-infected cells.

What is the difference between CD4+ T cells and CD8+ T cells?

CD4+ T cells are known as “helper” cells, and they are involved in almost all adaptive immune responses. They use cytokine signaling to help activate B cells that secrete antibodies and macrophages to destroy microbes. CD4+ T cells also help activate CD8+ T cells to kill the target cells.

CD8+ T cells (Cytotoxic T Cells), called “killer” cells, directly kill virus-infected and cancerous cells and use small signaling proteins called cytokines to recruit other cells when neutralizing these foreign threats.

Regulatory T cells are another class of T cells. They can distinguish between foreign cells and the body’s own cells to prevent the immune system from attacking itself.

How are T cells activated?

Once T cells are mature and leave the thymus, they circulate throughout the bloodstream until they identify to their antigen on the surface of a foreign invader. When the T cell receptor (TCR) binds to the antigen, activation begins. Mature T Cells which are not activated are Naïve T Cells.

How do T cells recognize antigens?

Each T cell has a unique T cell receptor (TCR) that recognizes a specific antigen.

TCRs recognize an antigen when they bind with major histocompatibility complex (MHC) molecules on the surface of other cells. There are thousands of TCRs on the surface of a T cell, which increases the chances of the T cell binding with an antigen.

What is T cell isolation?

T cell isolation is a process used to separate T cells from a heterogeneous mixture of cell types within a variety of complex biological samples, such as blood or tissue.

Once T cells are isolated, they can be characterized, modified, or used for experimentation. One common application is for T cell therapy research, which involves genetically modifying T cells and studying their ability to kill cells of interest. CAR-T cell therapy is a common treatment that involves genetically modifying T cells to improve their specificity toward cancer cells.

What are the methods of T cell isolation?

The same cell separation methods used for T cell isolation can be used for B cell isolation. Some common methods used for T cell isolation are magnetic cell sorting, density gradient centrifugation, and microfluidic cell sorting.

One method is selection. Positive selection is when T cells are targeted by the removal mechanism and retained for downstream analysis. On the other hand, negative selection is when other cell types are removed to leave the T cells untouched.

T cell depletion is another approach, where a single cell type—in this case, T cells—is removed from a biological sample to enrich all other remaining cell types.

What is the difference between T cells and B cells?

There are two types of lymphocytes: T cells and B cells. They are both critical parts of the immune response and are interconnected, because T cells are required to activate B cells.

While both B cells and T cells are involved in triggering the immune response, the main difference between the two is that T cells can only recognize viral antigens on the outside of infected cells and B cells can only identify the surface antigens of the infectious agents themselves.

What diseases affect T cells?

While some T cell diseases can be caused by illnesses, others are inherited.

Diseases involving a high T cell count include the following:

  • STIs such as syphilis
  • Viral infections
  • Parasitic infections
  • Tuberculosis
  • Blood cancer

A low T cell count could be a sign of an autoimmune disease, a nerve disease, or a disease that weakens the immune system, such as HIV. Additionally, lymphocytopenia (also known as lymphopenia) can be caused by a low lymphocyte count.

New treatments such as TCR therapy are being introduced to help T cells.

Is it possible to isolate DNA from T cells?

Yes. DNA is encased in the nucleus of cells, and T cells have nuclei.

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