Reduced Plasma IL-40 and Total IgA Levels in Patients with Substance Use Disorders: Indicators of Impaired Humoral Immune Response

BackgroundSubstance use disorders (SUDs) continue to be a public health challenge of significant importance. The immunomodulatory effects of substances of abuse have been extensively studied but there is a dearth of information on their effects on plasma interleukin-40 (IL-40) level, a biomarker of B cell activity, and its consequent effects on plasma total IgA level in patients with substance use disorders (SUD). Therefore, the plasma levels of IL-40 and total IgA in SUD patients were determined in this study. MethodsNinety adults comprising 50 SUD patients and 40 controls were enrolled into this case-control study. The SUD patients were stratified into groups based on the number of substances they abuse and plasma levels of IL-40 and IgA were determined using ELISA. ResultsMarijuana was the most abused substance (68.0%) and majority of the SUD patients (64.0%) were polydrug users. The median plasma IL-40 level was significantly lower in SUD patients compared with the controls. Similarly, the median plasma total IgA level was significantly lower in SUD patients compared with the controls. However, there were no significant differences in the plasma levels of IL-40 and IgA in SUD patients who abuse single substance, two substances, and three or more substances. The plasma IL-40 level had significant positive correlation with IgA in SUD patients. ConclusionSubstance use disorder is associated with impaired humoral immune function, but the dysregulation appears not to be influenced by poly-drug use. Studies evaluating the mechanisms underlying humoral immune impairment in patients with substance use disorder and its potential clinical implications are suggested.