The first description of CD20+ T cells in humans dates back, to our knowledge, to 1993, when two distinct populations of CD20-reactive lymphocytes, previously described using commercial CD20 mAb reagents in routine immunophenotyping [14,15], were characterized in HD by demonstrating that the CD20 marker was expressed at either high or low density, hence defined as CD20bright and CD20dim population, respectively. Here, MS4A1 is linked to Huntington disease.