Serum immunoglobulin levels and humoral immune competence in coalworkers

Serum immunoglobulin (Ig) levels were measured in 788 coalworkers and 121 nonmining controls for comparison with the radiological category of pneumoconiosis after taking into account age and smoking habit. In addition a simple assessment of humoral immune competence was made by estimating the titre of serum antibody against the common gut commensal Escherichia coli. Smoking was found to depress serum IgA and IgM whilst levels of IgG and IgA increased slightly with age. Men with radiological signs of coalworkers pneumoconiosis (CWP) had significantly raised levels of IgA and IgG with increasing pneumoconiosis category. Even coalworkers with less than category 1 simple pneumoconiosis had raised levels of IgA, suggesting that increased production of this immunoglobulin occurs before radiologically identifiable pathological changes have occurred in the lung tissue. No association between reduced humoral immune competence and radiological category of pneumoconiosis was found. Whether high Ig levels in men exposed to coal dust are merely a passive response to dusted lung tissue or whether they indicate that an immunological process is important in the development of pneumoconiotic lesions remains uncertain.