B and T lymphocytes both interact with each other because they are both attacking the same antigen. However the T cells influence and help the B cells. There are 2 mechanisms which explain the interaction which are:
1. The t cells interacting with the antigen produces a soluble factor. The B cells then react with the antigen and its associated soluble factor and start producing antibodies.
2. The t cells and B cells both interact with the same antigen. This allows the T cells to send interleuking signals to the B cells to start producing antibodies.
Its a bit late but its for my revision lol.