In an earlier study evaluating the expression of PD-1 and T-cell immunoglobulin and ITIM domain (TIGIT) in normal and diseased tissues we had found the highest TIGIT and PD-1 levels among CD4+ and CD8+ T-lymphocyte located in the germinal centers of Hashimoto thyroiditis [35]. Here, CD4 is linked to Hashimoto thyroiditis.