High anti-phosphorylcholine antibody levels and mortality associated with pneumonia.

Phosphorylcholine is an immunodominant determinant of pneumococcal teichoic acids. Antibodies to phosphorylcholine are naturally occurring in man and decline in amount with age. Since antibodies to phosphorylcholine are markers of the immune responsiveness to polysaccharides and since anti-polysaccharide antibodies are highly protective against most bacterial pneumonia we expected a higher rate of pneumonia in elderly individuals with low levels of antibodies to phosphorylcholine. The relationship between the levels of antibodies to phosphorylcholine and mortality was analyzed prospectively in a representative sample of elderly individuals. A significant anti-phosphorylcholine antibody response occurred in a subgroup of the probands. There was a strong association (p less than 0.0001) between high levels of antibodies to phosphorylcholine in the serum at 70 years of age and pneumonia related death up to 14 years later. A similarly strong association was not observed between mortality and the antibody titer to another naturally occurring polysaccharide antigen: the blood group B antigen. Furthermore, there was no association between mortality due to diseases other than pneumonia and the levels of antibodies to phosphorylcholine. The association between antibody levels and subsequent fatal pneumonia provides a means of detecting individuals at risk for pneumonia-related death.