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Ectopic T cell receptor expression causes B cell immunodeficiency in transgenic mice

Mice expressing transgenic T cell receptors (TCR) are used to explore important questions in immunity. However, transgene expression may have unexpected effects. We previously reported a B cell immunodeficiency, comprising decreased B cell numbers and diminished antibody responses, in mice that express a transgenic TCR specific for nicotinic acetylcholine receptor; the mice were generated using cassette vectors designed specifically for transgenic TCR expression [see Kouskoff et al. J. Immunol. Methods 1995. 180: 273–280]. We now show data suggesting that this defect is due to the expression and accumulation of TCR α and β chains inside B cells and induction of an endoplasmic reticulum stress response, causing apoptosis at the pre B‐I and later B cell stage. Thus, inappropriate transgene expression can profoundly affect B cells, leading to a previously undescribed mechanism of immunodeficiency.