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.
Cytotoxic T cells. Cytotoxic T cells (TC cells, or CTLs) destroy virally infected cells and tumor cells, and are also cause much of the damage in in transplant rejection and autoimmune diseases. These cells are also known as CD8+ T cells since they express the CD8 glycoprotein at their surface.