AQA A Level Biology复习笔记2.5.4 The T Lymphocyte Response

• Lymphocytes are another type of white blood cell
• They play an important part in the specific immune response
• They are smaller than phagocytes
• They have a large nucleus that fills most of the cell
• They are produced in the bone marrow before birth
• There are two types of lymphocytes (with different modes of action). The two types of lymphocytes are:
  • T-lymphocytes (T cells)
  • B-lymphocytes (B cells)

   

T-lymphocytes and the cellular immune response

• Immature T-lymphocytes leave the bone marrow to mature in the thymus
• Mature T-lymphocytes have specific cell surface receptors called T cell receptors
• These receptors have a similar structure to antibodies and are each specific to one antigen

The maturation of T-lymphocytes – some become helper T cells and others become killer T cells

• T-lymphocytes are activated when they encounter (and bind to) their specific antigen that is being presented by one of the host’s cells (host cells being the human’s own cells)
• This antigen-presenting host cell might be a macrophage or a body cell that has been invaded by a pathogen and is displaying the antigen on its cell surface membrane
• These activated T-lymphocytes (those that have receptors specific to the antigen) divide by mitosis to increase in number (similar to the clonal selection and clonal expansion of B-lymphocytes)
• These T-lymphocytes differentiate into two main types of T cell:
  • helper T cells
  • cytotoxic T cells(also known as killer T cells)