Lysozyme and other measures of immunity in young, mature, and aged rats

Lysozyme, peroxidase, serum proteins, and immunoglobulins were measured in young (1 month), mature (13 months), and aged rats (25 months). Circulating levels of immunoglobulins G and A increased with maturity as did the globulin fraction of serum protein. Concentration of the bactericidal enzyme, lysozyme, was significantly increased in serum and kidney and significantly decreased in spleens of aged rats.