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 Cells alive