CD22 and leukemia: Eleven dogs were diagnosed with “mixed lineage” leukemia based on flow cytometric expression of myeloid-associated markers (n = 5) or positive cytochemical staining reactions combined with positive staining for B (CD21 or CD22) or T (CD3 or 5) lymphoid-associated antigens on flow cytometric analysis (n = 6) (Table 6, Supplementary Table S6).