Detection of potassium channel KIR4.1 antibodies in Multiple Sclerosis patients

The presence of KIR4.1 antibodies has been proposed to be a characteristic of Multiple Sclerosis (MS). This could have a significant impact on disease management. However, the validation of the initial findings has failed till date. Conflicting results have been attributed to difficulties in isolating the lower-glycosylated (LG) KIR4.1 expressed in oligodendrocytes, the putative target antigen of autoantibodies. The aim of this study is to verify the presence of KIR4.1 antibodies in MS patients, by independently replicating the originally-described procedure. Assay procedure consisted of KIR4.1 expression in HEK293 cells, 3-step elution to isolate LG-KIR4.1 in elution fraction 3, and ELISA. Sera of 48 MS patients and 46 HCs were studied in 21 working sessions. In a preliminary analysis, we observed different KIR4.1 antibody levels between MS patients and Healthy Controls (HCs). However, a high variability across working sessions was observed and the sensitivity of the assay was very low. Thus, stringent criteria were established in order to identify working sessions in which the pure LG-KIR4.1 was isolated. As per these criteria, we detected LG-KIR4.1 antibodies in 28% of MS patients and 5% of HCs. Unlike previous findings, this study is in agreement with the original report. We propose further efforts be made towards the development of a uniform method to establish the detection of KIR4.1 antibodies in MS patients.