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Modulation of cytokine production by social environment and susceptibility to infections

Elodie Merlot 
Abstract : The immune consequences of environmental stress are complex and difficult to predict. Stress affects the immune system either at the level of innate immunity, through the alteration of inflammatory reactivity, or at the level of acquired immunity, through the modulation of Th1 and Th2 cytokines. In social species, social environment contributes to the development and expression of diseases. The social position in a group modulates susceptibility to infections. However, the endocrine and immune mechanisms involved in these differences are not known. Instability in the social organization generates a severe stress of which immune consequences are still controversial. The purposes of this thesis are (1) to describe the influence of social status on the endocrine and immune systems, (2) to specify the effects of social stress on cytokine production and susceptibility to infections and (3) to look for possible sources of variability in the immune consequences of social stress. Mixing piglets after weaning transiently increases salivary cortisol and modifies behavior but does not affect blood lymphocyte reactivity. The following experiments used a procedure of chronic social defeat in mice. Results show an influence of social status. In the absence of stress, dominants show higher basal corticosterone levels and specific response to tuberculin than subordinates. After social defeat, dominants are more affected. Social defeat increases inflammatory reactivity but does not clearly modify the balance between Th1 and Th2 cytokines production and does not affect the development of specific immunity against a mycobacterial infection. Immune effects of social defeat can be observed only when the stress involves significant fights and injuries. Our work shows that the response to stress depends on individual social experience, in particular on social status. Furthermore the immune consequences of stress depend on recent immune experience. Indeed a systemic inflammatory challenge inhibits the release of plasma inflammatory cytokines in response to a subsequent psychological stress.
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Submitted on : Friday, July 23, 2004 - 8:00:00 AM
Last modification on : Thursday, March 18, 2021 - 12:56:03 PM
Long-term archiving on: : Thursday, September 30, 2010 - 6:15:26 PM


  • HAL Id : pastel-00000790, version 1



Elodie Merlot. Modulation of cytokine production by social environment and susceptibility to infections. Sciences of the Universe [physics]. INAPG (AgroParisTech), 2003. English. ⟨NNT : 2003INAP0021⟩. ⟨pastel-00000790⟩



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