In this paper we introduce a new concept termed "teacher immunity". We propose that this immunity emerges from the accrued experiences of coping with disturbances and problems in stressful teaching environments, and that it functions as an indispensable protective armor allowing language teachers to survive the unavoidable hassles of classroom practice. We draw parallels with biological immunity and established constructs in psychology, while describing the development of this emergent immunity through the framework of self-organization from complexity theory. We further argue that, similar to biological immunity, teacher immunity can have potential negative consequences if it develops into a maladaptive form that is associated with a rigid and conservative practice as well as a general resistance to methodological change or innovation. Therefore, the article concludes by outlining how counterproductive teacher immunity can be "rebooted" through a three-step sequence that involves triggering the process through awareness raising, familiarizing teachers with productive coping strategies, and encouraging the formation of appropriate narratives that stabilize the transformation.