CD3, CD4, and CD8 all these tests are performed on a sample of blood to measure the level of CD3, CD4, and CD8 in the blood. The test is performed to confirm the T cell lymphoma and also during the treatment and after the treatment of the T cell lymphoma. Lymphoma is caused by lymphocytes a specific type of WBC. Lymphocytes can be either T cell or B cells. In the mature T cell (CD3) population the T cells can be either helper T cells (CD4) or suppressor T cells (CD8). Therefore in the test for lymphocyte the CD4 cells plus the CD8 cells should be equal to CD3. This way you can calculate the CD3 absolute count. The test is used to evaluate the immune system of a person diagnosed with Human Immunodeficiency Virus (HIV) infection.