Chronic Stress Down Regulate IFNγ in Cytotoxic Cells of the Common Carp (Cyprinus Carpio)

The involvement of cytotoxicity in the negligible levels of IFNγ during chronic stress in common carp (Cyprinus carpio) was studied by measuring leukocyte levels using flow cytometry and immune components mRNA involved in cytotoxicity using real-time qPCR. Acute and chronic oxidative stresses were generated by different regimes of carp exposure to environmental air. Results revealed that CD4 and CD8a cell levels were both about 7% of the peripheral blood leukocytes, while the ratio between CD4 and CD3γ/δ mRNA was 1:4 and the ratio between CD3ξ and CD3γ/δ mRNA was 4:6.

Under conditions of acute stress, cytotoxicity did not take a part whereas, under conditions of chronic stress, the CD3γ/δ mRNA increased only in the first week (171%), while the mediator of proteolysis, NCCRP1 mRNA increased to peaks of 533%, and remained high during 22 days of chronic stress. The regulators of Th1 cells (CD4, CD3ξ, and Tbet mRNA) and the apoptotic cytokines (FasL, granzyme and NK- lysin mRNA) decreased continuously (up to 14%, 41%, 29%, 23%, 29%, and 26% respectively), during 22 days of chronic stress.

In conclusion, it is suggested that most of the lymphocytes in carp belong to the nonspecific immunity, while the γ/δ T cells are dominant. In acute stress, cytotoxicity probably does not participate in the ‘fight or flight’ process, while in the case of chronic stress; there is a deterioration of Th1 cells, suppression of the apoptotic processes as well in the total suppression of INFγ production.

Keywords: cytotoxicity, gamma/delta T cell, acute/chronic stress, Th1 cell, NCCRP1, CD3zeta.