Log-Normal ELISPOT spot size distribution permits count harmonization among different laboratories

Introduction ELISPOT assays are primarily used to detect the number of T cells that respond to a given antigen. With that number being absolute for any given donor sample, ELISPOT counts should be similar between laboratories, if subjectivity in counting is avoided. Due to the differences in spot sizes ranging from microns to millimeters, setting cut offs for minimal and maximal spot sizes will lead to substantial variability between investigators when determined subjectively, irrespective of experience. In contrast, if spot size distributions would follow predictable statistical functions, objective gating decisions could be made using common standards, eliminating subjective calls of the counting process. This study aims to determine if ELISPOT size distribution follows predictable statistical distributions and therefore if ELISPOT counting can be made objective based on statistical principles.