Age‐related changes in immunoglobulin isotypes in whole and parotid saliva and serum in healthy individuals

Mucosal infections account for the majority of infections seen in elderly people, but little is known of whether mucosal immunity decreases with age. The objective of this study was to investigate the effect of age on the levels of salivary and serum immunoglobulins and the salivary immunoglobulin secretion rates in a healthy adult population. Healthy subjects (116 total) were divided into the following age groups: 20-39; 40-59; 60-79 and >80 years. Unstimulated (resting) whole and stimulated parotid saliva and serum were collected from all participants. Salivary and serum immunoglobulins were quantified by enzyme-linked immunosorbent capture assays. The levels of serum immunoglobulin G (IgG) and IgM were significantly reduced in the oldest age group, whereas no significant reduction in the level of IgA with age was observed. The IgG and IgA levels in whole saliva increased significantly in the oldest age group D, but no changes were detected in IgM levels. No significant changes in any immunoglobulin levels with age were found in parotid saliva. However, significant reductions in the secretion rates of IgA and IgM, but not IgG, in whole saliva were detected in the oldest age group. No significant changes in the secretion rates in parotid saliva were found with age. Our results demonstrate a decline in immunoglobulin concentrations with increased age, which may contribute to the increased susceptibility of elderly individuals to infectious diseases.