A common problem for the purple leaf plum tree is blossom blight, in which first the flowers, then young leaves, turn brown and wither, according to Grow Fruit by Alan Buckingham.
Once activated, helper T cells start to divide and to produce proteins that activate B and T cells as well as other immune cells. The killer T cell is specialized in attacking cells of the body infected by viruses and sometimes also by bacteria.
The body contains millions of different T-cells, each able to respond to one specific antigen. The T-cells secrete interleukin 2. Interleukin 2 causes the proliferation of certain cytotoxic T cells and B cells. From here, the immune response follows 2 paths: one path uses cytotoxic T cells and the other uses B cells. Cytotoxic T Cell Pathway The cytotoxic T cells are capable of recognizing antigens on the surface of infected body cells.