Influence of cadmium on the immune system. Description of stimulating reactions

Allergic diseases, atopy, bronchial asthma and chronic obstructive bronchitis are diseases which can directly or indirectly be traced to changes in the function of the immune system. Epidemiological studies have shown that these allergic diseases have increased in the course of time and that the incidence of obstruction of the respiratory system is clearly higher in polluted regions than in comparable control areas. These diseases are mainly the result of a comprehensive influence on the immune system. The present study describes the influence of pollutants on the behavior of cytokines which cannot be directly traced to an allergen or antigen in order to be able to explain various immunological or pseudo-allergic processes. We have isolated and cultivated PBMC from six donors and exposed them to different concentrations (5, 25, 50 and 100 mumol) of cadmium chloride. After incubation of cells with cadmium, different genes of cytokines were detected on the basis of mRNA by RT-PCR. Hsp70 can be detected in a relatively brief period following stress and there is an excellent correlation between heavy metal dose (stress) and expression of hsp70. In the case of IL-1, and TNF-alpha low concentrations of cadmium chloride increase the expression of these genes, whereas this effect is less noticeable with higher amounts of cadmium. After only one hour of exposure to heavy metals, large volumes of mRNA of IL-6 have been detected. IFN-gamma only reacts at high concentrations of cadmium. Heavy metals may influence immunocompetent cells so that they release several cytokines which may act on a large variety of cells in terms of a proinflammatory reaction. The influence of cytokines as well as the pollutants themselves on fibroblasts, endothelial cells as well as macrophages explains a number of processes which cannot be explained by allergical reactions. At low concentrations, cadmium is able to stimulate the immune system, while at higher concentrations inhibitory and suppressive reactions were observed.