T4 lymphocytes, also known as CD+4 cells and T4 helper cells, are a type of lymphocyte. Lymphocytes are a type of white blood cell produced by the immune system. A T4 lymphocyte is part of the adaptive immune system and has the specific task of helping T cells mature to fight foreign antigens that invade the body.
The immune system is divided into two groups: the adaptive and innate immune system. Adaptive immune responses, called acquired responses, develop throughout a person’s lifetime and work to create immunity to each antigen the body is exposed to, creating a memory for future invasions. Innate immune responses are immediate responses by the immune system to prevent infection starting from the moment of exposure. Natural killer cells are part of the innate immune system. T cells and B cells are part of the adaptive immune system. Helper T4 lymphocytes are part of both immune responses because they help all of the cells of the immune system but are more beneficial to the adaptive immune system.
A T4 lymphocyte is a type of T cell. Although T cells in general are part of the adaptive immune system, T4 lymphocytes are different. They are particularly beneficial in triggering the maturation of T cells. T4 cells start out in bone marrow but cannot mature until they interact with the thymus. A T4 cell is a T lymphocyte, known as a T cell, that has a special surface molecule called CD4 and a T4 surface protein, for which it is named.
Cell-mediated immunity is the branch of adaptive immune response that relies on T cells to operate instead of B cell antibodies. T4 lymphocytes help trigger the production of more T cells to regulate the adaptive immune system’s responses. In order to accomplish this, T4 cells have to be activated by a special protein that cells produce called cytokines. Once these proteins trigger cell activation, the T4 cells can begin working within the adaptive immune system.
Blood tests are used to monitor T4 lymphocytes. Increases in T4 cell counts can be a result of a viral infection. Decreases in cell counts can be caused by an infection following a surgical procedure. Immune disorders, such as the human immunodeficiency virus (HIV), can also cause low T4 cells counts as the virus invades and kills the T4 cells.
T4 lymphocytes are only a small representation of the different types of white blood cells that the body produces. Although they are just one type, they have an important role. Without T4 cells, T cells cannot mature and protect the body. While the innate immune system has the ability to protect with each instance of foreign antigen invasion, the adaptive immune system and T cells must provide long-term protection against the antigens to which the body is exposed.