An increase in basophils in a case of acute myelomonocytic leukaemia associated with marrow eosinophilia and inversion of chromosome 16

Simultaneous expression of CD13, CD22 and CD25 is related to the expression of Fc epsilon R1 in non-lymphoid leukemia

Like CD19 or CD56, CD22 in non-lymphoid leukemia has been considered an aberrantly expressed antigen. CD22 had been believed to be restricted to B lymphoid, however, it was also found to be expressed in human basophils. Mature basophils are unique granulocytes expressing CD13, CD22 and CD25. To estimate whether the expression of CD22 in non-lymphoid leukemia is aberrant or related to basophilic character, we analyzed 108 patients with primary and secondary leukemia. Among non-lymphoid leukemias, surface CD22 expression was more frequently observed in peroxidase-negative AML and secondary leukemia, and was usually observed simultaneously with CD13 and CD25. Samples obtained from 17 cases were further analyzed, and all the Fc epsilon R1-positive cases were observed in peroxidase-negative AML and secondary non-lymphoid leukemia, and mostly expressed CD13, CD22 and CD25. Therefore, surface CD22 expression in non-lymphoid leukemia was thought to relate to basophilic phenotype in some cases. Like CD22, some of the so-called aberrantly expressed antigens may not actually be aberrant, but are expressed in a stage of differentiation and maturation of progenitors. Moreover, CD22 may be one of target molecules for treatment of CD22-positive, poorly prognostic leukemia.