Hodge et al. [23] also looked at perforin and granzyme B expression by peripheral blood T lymphocytes, and unlike the findings of this study and of others on the expression of activation markers by peripheral T lymphocytes [19-21], they showed that the percentage of peripheral CD3+ and CD8+ cells expressing perforin and granzyme B is greater in COPD than in normal subjects. Here, PRF1 is linked to chronic obstructive pulmonary disease.