Disease

B-cells and antibodies:

• B-cells are white blood cells that produce antibodies.
• a antibody is a protien molecule that can bind specifically to a antigen.
• each B-cell has antibody molecules on its surface and can secrete soluble antibodies into its surroundings.

T-cells and receptors:

• T-cells are white blood cells that have receptor protiens on their surfaces.
• receptor protiens have only one binding site and are only found on the surface of T-cells.
• receptor protiens bind specifically to antigens to form antigen-receptor complexes.

helper T-cells and clonal selection:

• the antigen presenting cell will encounter a heplper T-cell with a matching receptor molecule, so the two can bind together.
• the tight binding stimulates the helper T-cells to release cytokines, which stimulate immature T and B-cells, when activated they divide by mitosis. this is clonal selection as only the selected cells are cloned.