A study examining the influence of TCZ on neutrophils function in vitro did not find increased apoptosis or phagocytosis of neutrophils.[34] Another study did find an impaired leukocyte trafficking to bone marrow, or function impairment.[35] A study by Moots et al, found that RA treated with TCZ had a higher rate of neutropenia, not resulting in increased infections rates.[36] In our study we did find an association between leukopenia and low complement levels, which might represent an up-stream effect of IL-6 blockade. This evidence concerns the gene IL6 and neutropenia.