Relationships between increased haptoglobin plasma levels and activation of cell-mediated immunity in depression

Recently, it was found that major depression is accompanied by an acute phase (AP) response with increased haptoglobin (Hp) plasma levels and various indices of systemic immune stimulation. The present study has been carried out in order to determine the relationships between hyperhaptoglobinemia and indices of systemic immune activation in severe depression. Toward this end, the authors investigated the relationships between Hp levels and number of leukocytes, monocytes, neutrophils, lymphocytes, and activated T lymphocytes (CD25⁺, HLA-DR⁺), in depression. Hp plasma levels were significantly higher in major depressed subjects as compared to healthy controls and minor depressives. There was a significant positive correlation between Hp levels and severity of illness. Hp plasma levels showed significant and positive relationships with the absolute number of leukocytes, neutrophils, monocytes, CD25⁺ and HLA-DR⁺ T cells. Up to 35% of the variance in Hp levels could be explained by the regression on the number of neutrophils and HLA-DR⁺ T cells. The results show that hyperhaptoglobinemia in major depression is significantly related to activation of cell-mediated immunity.