Tag: cells in immune system

MHC class II molecules bind peptides from antigens processed in organelles. These extracellular antigens, such as whole bacteria, engulfed by APCs via phagocytosis or endocytosis are enclosed in an intracellular vesicle. This vesicle containing peptides is fused with another vesicle containing MHC class II proteins. Upon fusion, the peptide is loaded onto MHC class II molecules, and the entire complex migrates to the cell membrane surface, where peptide-specific CD4 T cells recognize it. Thus the correct answer is option A.

Helper T-cells secrete signaling molecules called lymphokines to coordinate the immune response. Killer T-cells (cytotoxic T-cells) secrete perforins, which create pores in the membranes of target cells to induce lysis.

• A T cell, or T lymphocyte, is a type of lymphocyte that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of a T-cell receptor on the cell surface. They are called T cells because they mature in the thymus. 
• The types of T-cells are killer cells (cytotoxic cells) which destroy virus-infected cells and tumor cells, and are also implicated in transplant rejection, helper T-cells which  assist other white blood cells in immunologic processes, including maturation of B cells into plasma cells and memory B cells, and activation of cytotoxic T cells and macrophages and suppressor T-cells which are crucial for the maintenance of immunological tolerance.
  

Bone marrow is a semi-solid tissue which may be found within the spongy or cancellous portions of bones. Bone marrow is the primary site of new blood cell production or hematopoiesis. Bone marrow is considered as a primary lymphoid organ which is involved in the production and early clonal selection of lymphocyte tissues. Bone marrow is responsible for both the production of T cells and the production and maturation of B cells. 

The thymus is a specialized primary lymphoid organ of the immune system. The T-cells are produced from the bone marrow. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts specifically to foreign invaders. The thymus is the largest and most active during the neonatal and pre-adolescent periods.

A T cell or T lymphocyte is a type of lymphocyte that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of a T-cell receptor on the cell surface. They are called T cells because they mature in the thymus. Most lymphocytes are short-lived, with an average life span of a week to a few months, but a few live for years, providing a pool of long-lived T cells (4-5 years) and B cells.

A T cell or T lymphocyte is a type of lymphocyte that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of a T-cell receptor on the cell surface. Lymphocytes such as B-cells and T-cells are produced in the bone marrow. They are called T- cells because they mature in the thymus.

• A T cell, or T lymphocyte, is a type of lymphocyte (a subtype of white blood cell) that plays a central role in cell-mediated immunity. T cells can be distinguished from other lymphocytes, such as B cells and natural killer cells, by the presence of a T-cell receptor on the cell surface. T-cells are originated from bone marrow and mature in the thymus gland. 
  
• There are 3 main types of T-cells in mammals. They are - cytotoxic cells ( destroy virus-infected cells and tumour cells), helper cells (assist other WBC in immunologic processes including maturation of B cells into plasma cells and memory B cells, and activation of cytotoxic T cells and macrophages and suppressor cells (stop  T cell-mediated immunity toward the end of an immune reaction).

An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The part of an antibody that binds to the epitope is called a paratope. These epitopes interact with the paratope based on the 3-D surface features and shape or tertiary structure of the antigen.

Antigenic determinants (epitopes) are the specific parts of an antigen recognized by the immune system. Both antibodies (secreted or B-cell receptors) and T-cell receptors are capable of binding to these determinants.