{'fraction_non_alphanumeric': 0.03626428216592151, 'fraction_numerical': 0.024341778440139097, 'mean_word_length': 5.313479623824452, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Generation of HER-2/neu-specific cytotoxic neutrophils in vivo: efficient arming of neutrophils by combined administration of granulocyte colony-stimulating factor and Fcgamma receptor I bispecific antibodies.

Abs are able to induce inflammatory antitumor responses by recruiting IgG Fc receptor (FcgammaR)-bearing cytotoxic effector cells. We recently described the capacity of the high affinity FcgammaRI (CD64) to trigger cytotoxic activity of neutrophils (PMN) during granulocyte CSF (G-CSF) treatment. To take advantage of FcgammaRI as a cytotoxic trigger molecule on PMN, two Ab constructs were prepared. We show that a chimeric human IgG1 Ab (Ch520C9) and an anti-FcgammaRI bispecific Ab (BsAb; 22x520C9), both directed to the proto-oncogene product HER-2/neu, interact with FcgammaRI. In addition, both Ab constructs mediate enhanced lysis of HER-2/neu-expressing tumor cells by G-CSF-primed PMN. However, engagement of FcgammaRI by Ch520C9 was inhibited by human serum IgG, thereby abrogating the enhanced Ch520C9-mediated cytotoxicity. BsAb 22x520C9, which binds FcgammaRI outside the ligand binding domain, effectively recruits the cytotoxic potential of FcgammaRI on G-CSF-primed PMN regardless of the presence of human serum. These results indicate that under physiologic conditions, serum IgG impairs activation of FcgammaRI-mediated cytotoxicity by conventional antitumor Abs. The IgG blockade can be circumvented with anti-FcgammaRI BsAbs. Using human FcgammaRI transgenic mice we demonstrate that BsAb 22x520C9 is able to engage FcgammaRI in vivo. BsAb 22x520C9 injected i.v. was readily detected on circulating PMN of G-CSF-treated transgenic animals. In addition, we showed that PMN remain "armed" with BsAb 22x520C9 during migration to inflammatory sites, and that after isolation such PMN specifically lyse HER-2/neu-expressing tumor cells. These results point to the possibility of targeting anti-FcgammaRI BsAbs to G-CSF-primed PMN in vivo, endowing them with specific anti-tumor activity.