Expression pattern of hybrid phenotype in adult acute lymphoblastic leukemia

We examined the expression of hybrid phenotype in 236 adults with acute lym phoblastic leukemia (ALL, 188 B-lineage ALL and 48 T-lineage ALL). In B-lin eage ALL, myeloid antigen (mAg) CD15 was concentrated in CD10-CD20-cases (4 9%); CD13 (42%). and CD33 (43%) in CD10 + CD20- cases. This trend had no co rrelation with the presence of Ph 1 or t(4; 11) chromosomal abnormality. T- cell antigen CD2, CD4, and CD7 was seen in four. four. and two cases. respe ctively, and CD4 + and CD7 + cases commonly expressed CD13 and/or CD33 (CD1 3/CD33). In T-lineage ALL, expression of mAg, CD11b (47%), CD13 (38%), CD15 (28%), and CD33 (51%) was restricted to CD3-cases. B-cell antigen CD19 was found in two cases with CD7 solely as T-cell antigen, and these cases poss essed CD13/CD33. CD21 was detected in three cases with CD3. In whole ALL, C D13/CD33 was associated closely with the presence of stem-cell antigen CD34 . and in T-lineage ALL, CD13/CD33 had a significant correlation with additi onal stem-cell features, such as HLA-DR, multidrug resistance I (MDR I) and c-kit gene expression. Our results suggest that immature ALL cells frequen tly express B + M +, T + M +, and occasionally B + T + M + phenotype; that B + T + M- phenotype is extremely rare: and that mAg expression in B-lineag e ALL is complicated as compared to T-lineage ALL.