Use of SRBC antibody responses for immunotoxicity testing

The production of antigen-specific antibodies represents a major defense mechanism of humoral immune responses and involves the cooperation and interaction of several immune cell types: antigen presenting cells, T helper cells, and B cells. Thus, there are several cells or cell products (e.g., interleukins) that may be altered following xenobiotic exposure, making assays that evaluate the production of antigen specific antibody a relatively comprehensive and sensitive assessment of immune function. Data suggest that the primary antibody response to SRBC may be one of the most sensitive endpoints available to assess chemical-induced alterations to the immune system. As a result, this endpoint has become the cornerstone of several recently established guidelines for assessing the potential immunotoxicity of xenobiotics. Five types of antibody may be produced in a humoral immune response (i.e., IgGs of various subtypes, IgM, IgD, IgA, or IgE). For immunotoxicity assessment, the focus has primarily been on assays that assess production of IgM antibodies. Although a number of assays have been developed to evaluate antibody production, the antibody forming cell (AFC) assay and enzyme-linked immunosorbent assay (ELISA) are the two most frequently employed to evaluate the potential immunotoxicity of a xenobiotic. In this manuscript, background information, as well as the pros and cons of each of these assays are discussed and detailed methods on conducting each assay are provided.