GZMK and rheumatoid arthritis: Granzyme A, B and perforin are related to cytolytic activity of CD8+ T cells in CTL, while granzyme K is expressed at higher levels in memory CD8+ T cells and therefore less related to CTL-mediated toxicity.33 We did not find differences in the frequencies of CD8+granzyme A+, CD8+granzyme K+, CD8+granzyme B+ or CD8+granzyme B+perforin+ T cells in peripheral blood (Figure 3b) and lymphoid tissue (Figure 3c) between HCs, RA-risk individuals and early RA patients.