Nobel Prize in Medicine, 2025 (Question : What are T-Cells? )

   T-Cells Nobel Prize in Medicine,2025 : 

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TOPIC : T-Cells Nobel Prize in Medicine,2025 

Introduction :  

Blood comprises of a fluid matrix, plasma and formed elements. Red blood cells (RBCs, erythrocytes), white blood cells (WBCs, leucocytes) and platelets (thrombocytes) constitute the formed elements. Blood of humans are grouped into A, B, AB and O systems based on the presence

or absence of two surface antigens, A, B on the RBCs. Another blood grouping is also done based on the presence or absence of another antigen called Rhesus factor (Rh) on the surface of RBCs. The spaces between cells in the tissues contain a fluid derived from blood called tissue fluid. This fluid called lymph is almost similar to blood except for the protein content and the formed elements 

Erythrocytes, leucocytes and platelets are collectively called formed elements and they constitute nearly 45 per cent of the blood 

Red Blood Cells : 

Erythrocytes or red blood cells (RBC) are the most abundant of all the cells in blood. A healthy adult man has, on an average, 5 millions to 5.5 millions of RBCs mm–3 of blood. RBCs are formed in the red bone marrow in the adults. RBCs are devoid of nucleus in most of the mammals and are biconcave in shape. They have a red coloured, iron containing complex protein called haemoglobin, hence the colour and name of these cells. A healthy individual has 12-16 gms of haemoglobin in every 100 ml of blood. These molecules play a significant role in transport of respiratory gases. RBCs have an average life span of 120 days after which they are destroyed in the spleen (graveyard of RBCs) 

White Blood Cells : 

1)Leucocytes are also known as white blood cells (WBC) as they are colourless due to the lack of haemoglobin. They are nucleated and are relatively lesser in number which averages 6000-8000 mm–3 of blood. 

2)Leucocytes are generally short lived. 

3)We have two main categories of WBCs – granulocytes and agranulocytes. 

4)Neutrophils, eosinophils and basophils are different types of granulocytes, while lymphocytes and monocytes are the agranulocytes. 

5) Neutrophils are the most abundant cells (60-65 per cent) of the total WBCs and basophils are the least (0.5-1 per cent) among them. Neutrophils and monocytes (6-8 per cent) are phagocytic cells which destroy foreign organisms entering the body. Basophils secrete histamine, serotonin, heparin, etc., and are involved in inflammatory reactions. 

6)Eosinophils (2-3 per cent) resist infections and are also associated with allergic reactions. 

7) Lymphocytes (20-25 per cent) are of two major types – ‘B’ and ‘T’ forms. Both B and T lymphocytes are responsible for immune responses of the body. 

Platelets :

Platelets also called thrombocytes, are cell fragments produced from megakaryocytes (special cells in the bone marrow). Blood normally contains 1,500,00-3,500,00 platelets mm–3. Platelets can release a variety of substances most of which are involved in the coagulation or clotting of blood. A reduction in their number can lead to clotting disorders which will lead to excessive loss of blood from the body. 

T-Cell Development : 

Lymphocytes are the unique cells of the immune system mediating adaptive immunity. These are the main cells exhibiting the cardinal features of the immune system, i.e., recognition, specificity, diversity and memory. 

The lymphocytes are divided into two major categories, B- lymphocytes and T-lymphocytes based on their origin and development. 

T-cells are vital components of cell-mediated immunity. T lymphocytes mediate a multitude of activities that include the effective establishment, maintenance, and restoration of integrity at the cellular level. T-lymphocytes mature in the thymus, a bilobed organ present just above the heart in the anterior mediastinum. 

Like B cells, these also bear surface receptors for the recognition of antigens. However, unlike B-cells, their receptor is not called immunoglobulins (antibody). T-cells have a heterodimer glycoprotein attached to their surface, called as T-cell receptor (TCR). T-cells differ in their functioning as compared to B-lymphocytes in the manner that B- lymphocytes can directly bind the antigen whereas T-cells require the help of major histocompatibility (MHC) molecules. 

The antigens to be recognised by the Tcell are first processed and presented with either class I or class II MHC molecule, on the surface of antigen-presenting cells (APCs) or other cells. Once activated by antigens, T- cells give rise to effector T-cells and memory T-cells. These lymphocytes exhibit a characteristic subpopulation of cells, Thelper (TH) cells and T-cytotoxic (TC) cells. Cytotoxic T- lymphocytes (CTL) fight against virus-infected cells or self-altered cells, tumor cells while T-helper cells are responsible for the secretion of cytokines and activation of B-cells. Another small population of T-cells has been shown to regulate the function of TH and TC cells. 

These cells are known as T-regulatory cells (Treg) or Tsuppressor cells. T-lymphocytes are said to be MHC-restricted. T-cells along with TCR express other distinct molecules, CD4 and CD8, in addition to other surface markers. However, CD4 and CD8 are never present on the same cell. 

T- cells that show CD4 are said to be restricted to interact with antigens presented in association with class II MHC molecules. Such CD4+ cells are T helper cells. The T-lymphocytes expressing glycoprotein CD8 on their surface are restricted to recognise antigens bound to class I MHC molecules. These CD8+ cells are T-cytotoxic cells. Being the key mediators of cell-mediated immunity, these cells are involved in fighting bacterial and viral infections. T cells are effective against tumour cells and graft tissue 

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All blood cells, including T-cells originate from the hematopoietic stem cells (HSCs) in the bone marrow . 

The HSCs are pluripotent cells that have the ability to give rise to a variety of cells under the influence of several cytokines and colony-stimulating factors (CSF) etc. An appropriate microenvironment is provided inside the thymus (a primary lymphoid organ) for their further development and maturation. 

The bone marrow of an adult individual consists of two subsets of HSCs, longterm HSCs recognised as lin− ckit+ Sca1+ CD150+ CD48− CD34− Flt3− and short-term HSCs (linlin− ckit+ Sca1+ CD150+ CD48− CD34+ Flt3− ). 

These cells in their course of development get committed to specific T-cell lineage in the thymus. Generally, in order to become mature Tor B-lymphocytes, the cells undergo a series of events including:- 

i) Commitment of progenitor cells 

ii) Proliferation of committed cells 

iii) Rearrangement of antigen receptor genes 

iv) Selection process 

v) Differentiation into distinct subpopulation 

Lymphocytes are the unique cells of the immune system mediating adaptive immunity. These are the main cells exhibiting the cardinal features of the immune system, i.e., recognition, specificity, diversity, and memory. The lymphocytes are divided into two major categories, B-lymphocytes and T-lymphocytes based on their origin and development. 

The TCR (T-cell receptor) is believed to experience elaborate somatic diversification resulting in a large repertoire of antigenic complementarity bearing receptors. In terms of composition, two polypeptide chains are and chains that together form the αβ T cell antigen receptor 

Like immunoglobulin, the antigen binding site lies in the complementarity determining region (CDR) portion of the variable region of both the polypeptide chains. Each variable domain in both chains consists of 3 such CDRs. The region that binds with antigen-MHC complex show maximum variability in amino acid residues. Another important feature of TCR is the presence of an invariant CD3 chain, which is required for the signal transduction process. 

All blood cells, including T-cells originate from the hematopoietic stem cells (HSCs) in the bone marrow. The HSCs are pluripotent cells that have the ability to give rise to a variety of cells under the influence of several cytokines and colony-stimulating factors (CSF) etc. An appropriate microenvironment is provided inside the thymus (a primary lymphoid organ) for their further development and maturation. 

The earliest thymic progenitors are termed as DN (double negative cells) cells consisting of 4 fractions viz., DN1, DN2, DN3 and DN4. These can be characterised by the absence of any CD4 or CD8 molecules and differential expression of CD25, CD44 and CD117 

The specific family of proteins namely Notch family are cell surface molecules involved in the commitment process and regulate the expression of target genes. The Notch receptors are

believed to be transmembrane glycoproteins which take care of the entire T-cell development process. 

A variety of cytokines are crucial to T-cell proliferation and commitment. These include stem cell factor (SCF), Flt3 ligand, and IL-7. 

There is an enormous diversity in antigen receptors of B and T-cells, the specificity of which is predetermined, before exposure to antigens. This repertoire of TCRs is due to the rearrangements in antigen receptor genes and is one of the crucial steps in lymphocyte development called V(D)J Recombination process 

The selection process is the second last step in the maturation of a functional T-lymphocyte. Its differentiation into immunocompetent cells depends on the intrathymic T-cell contact with MHC molecules. It results in two important events in the thymus; some T-cells are positively selected, transforming into specifically reactive thymocytes. Secondly, those T-cells with high affinity towards MHC molecules are negatively selected. 

Research: 

Extensive studies have been done to study the receptor molecule of Tlymphocyte. Importantly, along with TCR, there was the simultaneous discovery of MHC molecules. A variety of approaches were employed to decipher the structure of TCR. One of the approaches involves identification of genes that are specifically expressed in T-lymphocytes. This led to the discovery of the gene, homologous to the immunoglobulin gene (Ig). Thus, there are similarities between TCR and immunoglobulin. However, dissimilarities also exist 

What is TCR ? 

T- cell receptor is a heterodimer consisting of two transmembrane polypeptide chains bound to the T-lymphocyte. The TCR is believed to experience elaborate somatic diversification resulting in a large repertoire of antigenic complementarity bearing receptors. In terms of composition, two polypeptide chains are and chains that together form the αβ T cell antigen receptor. 

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What is Thymus ? 

The thymus gland is a lobular structure located between lungs behind sternum on the ventral side of aorta. The thymus plays a major role in the development of the immune system. This gland secretes the peptide hormones called thymosins.

Thymosins play a major role in the differentiation of T-lymphocytes, which provide cell-mediated immunity. In addition, thymosins also promote production of antibodies to provide humoral immunity. Thymus is degenerated in old individuals resulting in a decreased production of thymosins. As a result, the immune responses of old persons become weak 

The thymus gland secretes thymosins which play a major role in the differentiation of T-lymphocytes, which provide cell-mediated immunity. In addition, thymosins also increase the production of antibodies to provide humoral immunity 

======================================================= Question : What are T cells?

There are two main types of lymphocytes – T cells and B cells. T cells are a type of white blood cells which are a vital part of the immune system. They focus on particular foreign substances. 

Question 2: What is the main function of the T lymphocytes? 

The primary function of T-lymphocytes is to protect the body from infections and also helps in fighting cancer. 

Question 3 : Where are T lymphocytes found? 

T-lymphocytes are mainly found in lymphoid organs such as tonsils, bone marrow and spleen, but they are also found in small quantities in lungs, intestines and skin. 

Question 4: What are the varieties of T cells and what are their functions? 

The two types of T cells are helper T cells and cytotoxic T cells. They function to identify the antigen and fight against them. 

Question 5 : What is the function of helper T cells? 

Helper T cells are functional in almost all the adaptive immune responses. They activate B cells to secrete antibodies and macrophages to destruct ingested microbes. Furthermore, they aid in activating cytotoxic T cells in killing target cells that are infected. 

Question 6 : What are killer T cells? 

Killer T cells are a type of immune cells which can destroy some cells such as cancer cells, foreign cells etc. These killer T cells can be separated from other blood cells which grow in labs and then are administered to a patient to destroy

cancer cells. These are a type of white blood cells and also referred to as cytotoxic T cells. 

Question 7 : What is the function of killer T cells? 

Killer t cells release cytotoxins to kill infected cells. These immune cells destruct foreign cells, cancer cells etc. 

Question 8 : T cells are produced in? 

T cells take origin in the bone marrow, they mature in the thymus. Question 9 : How do T cells recognize antigens? 

Every T cell carries a T cell receptor or TCR which is unique to it. TCR identifies a particular antigen when it binds with the MHC (Major histocompatibility complex) molecules on the surface of other cells. 

Question 10 : What are the antigens recognized by T cells? 

            T cells are said to have dual specificity. They identify peptide antigens seen            on     MHC molecules as well as self-major histocompatibility complex molecules (MHC I or II). 

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Question: In 2025 , who are given Nobel Prize in Medicine or Physiology ?

Ans : Mary E . Brunknow, Fred Ramsdell and Shimon Sakaguchi 

Question : Why Mary E . Brunknow, Fred Ramsdell and Shimon Sakaguchi are selected for Nobel Prize for Medicine or Physiology in 2025 ? How their research helping ?

Ans : For their groundbreaking discoveries concerning peripheral immune tolerance that prevents the immune system from harming the body. 

Their discoveries have laid the foundation for a new field of research and spurred the development of new treatments, for example for cancer and autoimmune diseases.

Question : The Nobel Prize in Medicine 2025 laureates identified which system ? 

Ans : The Nobel Prize laureates identified the immune system’s security guards, regulatory T cells, thus laying the foundation for a new field of research. The discoveries have also led to the development of potential medical treatments that are now being evaluated in clinical trials. 

Nobel Prize in Medicine or Physiology 2025 : 

The body’s powerful immune system must be regulated, or it may attack our own organs. Mary E. Brunkow, Fred Ramsdell and Shimon Sakaguchi are awarded the Nobel Prize in Physiology or Medicine 2025 for their groundbreaking discoveries concerning peripheral immune tolerance that prevents the immune system from harming the body. Their discoveries have laid the foundation for a new field of research and spurred the development of new treatments, for example for cancer and autoimmune diseases.