Regulatory Position

Lymphocyte phenotyping is not required for registration of chemicals under FIFRA, TSCA, and the FDA's CFSAN. Although not currently required for European registration, phenotyping may be part of the revised guidelines suggested by the RIVM of the Netherlands.

Ex vivo proliferation of T cells is the endpoint of surface interactions and intracellular signaling. Proliferation measurements serve two purposes. Assessment of the nonspecific proliferative capacity can be determined by exposure to mitogens such as phytohemagglutinin or concanavalin A. When the mitogens are used over a dose range, subtle decrements in proliferation can be detected. The capacity of memory T cells to proliferate can be probed by exposure to tetanus toxoid, mumps, or Candida albicans. Most subjects have memory cells directed toward one or more of these preparations.

The NTP evaluated lymphocyte proliferation assays for inclusion in a proposed immunotoxicity screen. Data from the multilaboratory comparison showed that proliferation assays were insensitive regarding detection of immune defects and not reproducible across laboratories (Luster et al., 1988).

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