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 Human Immunodeficiency Virus (HIV) seems to only infect the CD4 (or T-helper) cells of the immune system.The CD4 cells are responsible for activating and directing other â¦ immune system cells.  HIV also infects macrophages and microglial cells that express the CD4 molecule on their surface.The virus can also infect a subtype of myeloid dendritic cells MDC-1. 12 people found this useful.he Human Immunodeficiency Virus (HIV) seems to only infect the CD4 (or T-helper) cells of the immune system.