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.
Art Connections. 1  Helper T cells release cytokines while cytotoxic T cells kill the infected cell. 2  Helper T cells are CD4+, while cytotoxic T cells are CD8+. 3  MHC II is a receptor found on most body cells, while MHC I is a receptor found on immune cells only. 4  The T cell receptor is found on both CD4+ and CD8+ T cells.