Anti-alpha4beta1 integrin antibody induces receptor internalization and does not impair the function of circulating neutrophilic leukocytes.

OBJECTIVE:A compelling strategy for treatment of spinal cord injury is the blockade of integrin-mediated leukocyte extravasation using a monoclonal antibody (mAb) against the alpha4 subunit of the alpha4beta1-integrin. However, little is known with respect to neutrophil function following anti-alpha4 mAb treatment. This study assessed the effects of anti-alpha4 mAb binding on neutrophil activation [reactive oxygen species production], function (phagocytic activity) and anti-alpha4-mAb/alpha4beta1-integrin-complex internalization. METHODS:Resting, primed or stimulated rat neutrophils were incubated ex vivo with anti-alpha4 mAb or isotype-control antibody. production, phagocytic activity, and anti-alpha4-mAb/alpha4beta1-integrin-complex internalization were determined by flow cytometry using dihydrorhodamine (DHR1,2,3), fluorescent microspheres, and indirect immunolabeling, respectively. RESULTS:Brief (0.5 h) incubation of resting, primed or activated neutrophils with anti-alpha4 mAb had no effect on duanyu1670 production and did not change neutrophil phagocytic activity. However, prolonged incubation (2 h), assessed only in resting neutrophils, increased duanyu1670 production. The anti-alpha4-mAb/alpha4beta1-integrin-complex was internalized after 1 h of anti-alpha4 mAb treatment and remained internalized up to 6 h. CONCLUSION:Neutrophil duanyu1670 production and phagocytic function remain unaltered after brief anti-alpha4 mAb exposure, demonstrating that use of this mAb as a treatment should not adversely affect important beneficial roles of these cells.

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