Yo is also known as Purkinje cell cytoplasmic antibody type 1 (PCA1) recognises a 34- and 62 kDa antigens expressed in the Purkinje neurones resulting in coarse staining pattern.

It is found predominantly in females and 90% of the time it is associated with carcinomas of the ovary or breast.
Yo antibody is a marker for cerebellar ataxia.

Image: Cytoplasmic staining of Purkinje cells in primate cerebellum