marrow, resulting in difficulty recognizing antigens and creating novel immune responses. This can be measured by decreased IgM and IgG antibody levels which are an indicator of immune suppression. T regulatory cells, which are critical to maintaining the correct level of response in the immune system, also appear to be altered by some agents. In the presence of certain immunotoxic substances, granulocytes of the innate immune system have also been observed to be damaged causing the rare disease agranulocytosis. Vaccine effectiveness can also be decreased when the immune system is suppressed by immunotoxic substances. In vitro T-lymphocyte activation assays have been useful when determining which substances have immunosuppressive properties. Hypersensitivity Hypersensitive or allergic reactions, such as asthma, are commonly associated with immunotoxic agents and the number of people exhibiting these symptoms is increasing in industrial countries. This partially due to the increasing number of immunotoxic agents. Nanomaterials are commonly absorbed through the skin or inhaled and are known for causing hypersensitive responses by recruiting immune cells. These nanomaterials are often encountered when a person is in contact with chemicals in an occupational, consumer, or environmental setting. Agents that are known for creating a hypersensitive response include poison ivy, fragrances, cosmetics, metals, preservatives, and pesticides. These molecules that are so small, they act as haptens and bind to larger molecules to induce an immune response. An allergic response is induced when T lymphocytes recognize these haptens and recruit professional antigen-presenting cells. IgE antibodies are important when looking at hypersensitive reactions but cannot be used to definitively determine the effects of an immunotoxic agents. Because of this, in vivo testing is the most effective way to determine the potential toxicity of nanomaterials and other agents that are believed to cause hypersensitivity. Autoimmunity Immunotoxic agents can increase the occurrence of immune system attacks on self molecules. Although autoimmunity mostly occurs as a result of genetic factors, immunotoxic agents such as asbestos, sulfadiazine, silica, paraffin and silicone can also increase the chance of an autoimmune attack. These agents are known for causing disturbances to the carefully regulated immune system and increasing the development of autoimmunity. Changes in the circulating regulatory and responder T cells are good indicators of an autoimmune response induced by an immunotoxic agent. The effects of autoimmunity have been examined primarily through studies with animal models. Currently, there is not a screen to determine how agents affect human autoimmunity, because of