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5.2 describe and explain the immune response in the human body in terms of:

describe and explain the immune response in the human body in terms of:

  • interaction between B and T lymphocytes
  • the mechanisms that allow interaction between B and T lymphocytes
  • the range of T lymphocytes types and the difference in their roles

Interaction between B and T lymphocytes

B and T lymphocytes interact as they are both attacking the same antigen. Helper T cells (see below) stimulate B cells and T cells to clone.

The mechanisms that allow interaction between B and T lymphocytes

The T lymphocytes that help B lymphocytes are called helper T cells (Th cells). If a B cell has an antigen on its surface, there is a risk that a T cell will recognise the antigen and attack it together with the B cell. This does not happen because T cells are able to recognise “self” molecules that are on the surface of B cells. Every person has their own particular “self” molecules, so there are millions of different B cells. They are like personal identity used to identify cells to T lymphocytes. This means that, in the case of organ transplants, T cells can recognise cells that have come from a different body and so help B cells to destroy them. Only identical twins have the same “self” molecules on their B cells.

The range of T lymphocytes types and the difference in their roles

Type of T cell Roles
killer T cells (Tc cells) attack and destroy macrophages that have engulfed an antigen. They produce cytotoxins.
helper T cells (Th cells) secrete chemicals that stimulate cloning in B and T cells
memory T cells remain in the body and reactivate quickly with subsequent infections by the same antigen
suppressor T cells stop the reaction when the antigen is destroyed

Antibody production (external website) Cells alive