A previous study on thymomas in MG patients indicated that OX40 expression in a fraction of activated CD4+ T cells may be upregulated in thymic tissues that are adjacent to germinal centers (GCs) and thymomas in MG, and OX40 may interact with OX40L in GCs to enhance anti-acetylcholine receptor antibody production in MG [16]. Here, CD4 is linked to thymoma.