Tag: immunity

• 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.
  
• B cells, also known as B lymphocytes are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system by secreting antibodies. B-cells bind to an antigen, receive help from a cognate helper T cell and differentiate into a plasma cell that secretes large amounts of antibodies and help in phagocytosis.
  
• Phagocytes are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.
  

• The acquired immunity involves two types of cells: B-cells and T-cells.T cells are involved in cell-mediated immunity, whereas B cells are primarily responsible for humoral immunity (relating to antibodies).
• Like all blood cells, B(B lymphocyte)- and T-cells9T-lymphocyte) are produced in the bone marrow. B-cells mature in the bone marrow and  T-cells travel through the bloodstream to the thymus gland and mature in the thymus gland.
• Hence B- and T-cells required for the immune system are produced in Bone marrow.
• So, the correct answer is 'Bone marrow'.

Adenosine deaminase deficiency or ADA deficiency is an autosomal recessive disorder that causes immunodeficiency. Gene therapy is a method to treat this. A functional ADA complementary DNA is inserted to the lymphocytes and then grown in an artificial culture. After the growth ADA cDNA is returned to the patient. 

The major histocompatibility complex (MHC) is a collection of genes coding for MHC molecules found on the surface of all nucleated cells of the body. There are two classes of MHC molecules involved in adaptive immunity, MHC I and MHC II. MHC I molecules are found on all nucleated cells, they present normal self-antigens as well as abnormal or non-self pathogens to the effector T cells involved in cellular immunity. In contrast, MHC II molecules are only found on macrophages, dendritic cells, and B cells; they present abnormal or non-self pathogen antigens for the initial activation of T cells.

There are 2 forms of MHC, namely MHC class I and class II proteins. They play important role in the adaptive immunity. They present peptides on the cell surface for recognition by T cells. Helper T cells are part of adaptive immunity. They recognize and activate B cells to secrete antibodies and macrophages to destroy foreign bodies. They also help activate cytotoxic T cells to kill infected target cells. B cells are part of humoral immune response. They recognize soluble antigens. Antigen-presenting cell (APC) are those cells with detects, engulfs and digests antigen. 

IgD provides the activation signals to the B cells by acting as antigen receptors on the B cell surface. The B cells on being activated begins the immune defense mechanism of the body. So, the correct option is 'IgD'.