Humoral and Cellular Effects of Stress-An Extensive Model System

The influence of stress on the immune system of the common carp (Cyprinus carpio) was studied by measuring leukocytes levels using flow cytometry and mRNA immune components by real time qPCR. Acute and chronic oxidative stresses were generated by different regimes of exposure of carp to environmental air. In acute stress, induced by single air exposure, the pro-inflammatory cytokines (IL1β, IL6 and TNFα) and the down-regulatory ones (IL10 and TGFβ) showed significant simultaneous elevations (515, 147, 373, 300 and 198% respectively). Following chronic stress (multiple air exposures) however, a drastic decline of 80%, in macrophages/monocytes, B-cells likes and plasma-cells like, occurred in peripheral blood. No statistical changes in IL6 and TNFα, as well as in IgM and C3s mRNA levels could be shown during this experiment. CD4 mRNA decreased up to 6% in the 2nd week of chronic stress and elevated only to 55% at the 3rd week Vs a temporal decline of up to 22% in CD8a mRNA at the 2nd week. The regulatory cytokines (IL10, FoxP3 and TGFβ) as well as the pro-inflammatory ones (IL1β and IL17) decreased significantly up to 0.06, 0.2, 5, 6 and 4% respectively, at the second week before being restored to normal at the 3rd week. Moreover, a persistent decrease, up to null levels, in the cytokines IFNγ2b, IL12b and IL8 was also revealed. These downregulations were suggested as a result of the impaired Th1 and/or cytotoxic cell function and, to a certain degree, the leukocytes mobilization. The above findings show that in contrast to the detrimental effects of chronic stress, in which cells and functions of acquired immunity were partially or completely impaired, the acute stress was found rather beneficial and in line with the known ephemeral “fight and flight” response.