In general CD8 refers to suppressor T cells, called cytotoxic T cells, also known as direct killing T cells in the immune response, CD8 normal value in 320-1250 microliter, CD8 high has the following significance: First, a marker of the hyperfunction of the human immune system, at this time in the human body infected with bacteria, viruses or other pathogenic microorganisms, such as mycoplasma and chlamydia infection, it will CD8 is high. Second, high CD8 may also occur in immune system diseases, such as rheumatoid arthritis, dermatomyositis, desiccation syndrome, and systemic lupus erythematosus, etc. CD8 values may also increase. Third, CD8 may also be high in rare diseases such as AIDS or tumors.