The effects of psychological stress on leukocyte subset distribution in humans: Evidence of immune activation

The aim of the present study was to examine the effects of academic examina tion stress on leukocyte subset distribution in university students. Thirty -eight university students had repeated blood collections for white blood c ell differentiation and flow cytometric assay of lymphocytic subsets a few weeks before and after (i.e. two baseline conditions) as well as the day be fore a difficult academic examination (i.e. stress condition). Flow cytomet ry was used to determine the number of peripheral blood mononuclear cells ( PBMC). in students, who were reactors to psychological stress (criterion ba sed on changes in the Perceived Stress Scale, PSS), but not in stress non-r eactors, a significant increase in the number of neutrophils, monocytes, CD 8(+), CD2(+)CD26(+), and CD2(+)HLA-DR+ T cells and CD19(+) B cells, and sig nificant reductions in the CD4(+)/CD8(+) T cell ratio were observed in the stress condition. There were significant and positive relationships between the stress-induced changes in perceived stress (PSS scale) and number of l eukocytes, neutrophils, CD2(+), CD2(+)CD26(+) and CD2(+)HLADR(+) T cells, a nd CD19(+) B cells. There were significant and negative relationships betwe en the stress-induced changes in the CD4(+)/CD8(+) ratio and the stress-ind uced changes in the PSS scale. Female students taking oral contraceptives s howed significantly higher stress-induced responses in number of leukocytes , neutrophils and CD19(+) B cells than male and female students without use of oral contraceptives. The results suggest that academic examination stre ss induces changes in the distribution of PBMC, which indicate immune activ ation and which are probably orchestrated by a stress-induced production of cytokines.