IL6 and B-cell chronic lymphocytic leukemia: In the first, they demonstrated that IRRs were associated with acute release of cytokines including interleukin 6 (IL6), tumour necrosis factor alpha (TNFA) and interleukin 8 (IL8).4 In the second, they correlated levels of CD20 expression with the development of IRRs, higher levels being associated with worse reactions.5 Of particular interest was that trisomy 12 was associated with a statistically significant increased risk of IRR; CLL with trisomy 12 exhibit higher levels of expression of CD20.