Question

The cells involved in defence against pathogens are

• A. Phagocytes
• B. T-lymphocytes
• C. B-lymphocytes
• D. All of the above

Answer 1

Answer: (D)

All of the above

• 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.
  

So, the correct answer is 'All of the above'.