[Effect of estrogens on the immune system with regard to bovine placental retention]

A survey of effects of estrogens on the immune system is given by a literature study. Changes in number and functionality of single populations of cells of the immune system are shown. Results often vary in dependence on the examined parameters, on the type of the used or measured estrogens, on the measuring methods and between the different species. Independent from that the capacity of the nonspecific cellular immune system seems to be increased under the influence of estrogens. Individuals with high estrogen levels showed an increase of the number of leucocytes and neutrophil granulocytes in the blood. In most of the functional studies on neutrophil granulocytes a suppressive effect of estrogens independent from the species could only be observed on the ability of directed migration. A stimulation or no effects of estrogens were reported on all the other parameters (random migration, phagocytosis, generation of reactive oxygen metabolites, cytotoxicity). Less is known about the effects of estrogens on mononuclear cells (lymphocytes, monocytes, natural killer cells). Mainly lymphocytes showed a decrease in their number in the blood and a suppressive effect of isolated cells in different species. It remains for further studies whether estrogens are of significance for bovine retained placenta by having effects on components of the immune system, and how significant they are.