Occurrence of protease-like catalytic activity in the polyclonal IgG in schizophrenia and bipolar disorder

Neuro-immune dysfunction and inflammation are said to be involved in the aetiology of major mental illnesses. This study describes the assessment of the protease-like catalytic function of serum IgG in psychiatric disorders, schizophrenia and bipolar disorder, along with healthy controls of Indian ethnicity. Systemic lupus erythematosus patients experiencing neuropsychiatry conditions were included as comparators for the comprehensive evaluation of IgG catalytic function. The catalytic activity of serum IgG was determined using the generic peptide substrate Pro-Phe-Arg-methylcoumarylamide, and then the apparent kinetic data was computed. Compared to healthy controls (n = 25), the activity of those with schizophrenia (n = 30) was found to be 11-fold higher. The neuropsychiatry lupus patients (n = 25) exhibited 2.7 times less activity than the schizophrenia group. The IgG activity of the bipolar patients’ (n = 30) were found to be 2.9 and 12 times higher than lupus and healthy controls. IgG activity showed a modest, no significant, link with PANSS positive and negative disease scores, in a subset of schizophrenia patients. The study’s findings express presence of catalytic antibodies in the blood as well as neuro-immune dysfunction in major psychosis disorders. In addition, subsets of schizophrenia patients indicate presence of autoimmune component in them.