Methods for predicting production of activating signals by cross-linked binding proteins

A method of predicting whether a therapeutic binding protein will induce a cytokine storm in a mammalian subject comprising the steps of:

• (a) obtaining a blood sample from the mammalian subject;
• (b) incubating the therapeutic binding protein with the blood sample, wherein the blood sample is a binding protein-treated blood sample;
• (c) determining the level of expression of at least one cytokine storm gene in the binding protein-treated blood sample;
• and
• (d) comparing the level of expression of the at least one cytokine storm gene in the binding protein-treated blood sample to the level of expression of the at least one cytokine storm gene in an untreated or a negative control-treated blood sample,
• wherein a level of expression of the at least one cytokine storm gene in the binding protein-treated blood sample substantially greater than the level of expression of the at least one cytokine storm gene in the untreated or negative control-treated blood sample indicates that the therapeutic binding protein will induce a cytokine storm in the mammalian subject.

A method of determining whether an anti-IL21R binding protein is a neutralizing anti-IL21R binding protein comprising the steps of:

• (a) contacting a first blood sample from a subject with an IL21 ligand;
• (b) determining a level of expression of at least one IL21-responsive gene in the first blood sample contacted with the IL21 ligand;
• (c) contacting a second blood sample from the subject with the IL21 ligand in the presence of an anti-IL21R binding protein;
• (d) determining the level of expression of the at least one IL21-responsive gene in the second blood sample contacted with the IL21 ligand in the presence of the anti-IL21R binding protein;
• and
• (e) comparing the levels of expression of the at least one IL21-responsive gene determined in steps (b) and (d),
• wherein a change in the level of expression of the at least one IL21-responsive gene indicates that the anti-IL21R binding protein is a neutralizing binding protein.