Age-related perforin expression in cytotoxic lymphocytes.

The percentage of perforin in NK cells (A) was rather constant as age increased. Perforin-containing CD8⁺ T cells (B) increased with age. In young children, especially in infants, the perforin content of CD8⁺ T cells was very low. Perforin-containing CD56⁺ T cells (C) also increased with age.