Immunological phenotypic pattern of acute lymphoblastic leukaemia in Egypt

We have performed immunophenotyping studies on 186 untreated cases of acute lymphoblastic leukemia (ALL) in an Egyptian population, using panels of monoclonal antibodies (mAb) and an avidin-biotin-immunoperoxidase detection system. Sixty-two of these cases were tested with a panel of mAb directed against the T-cell markers CD2, CD4, CD8, B-cell markers CD20, kappa and lambda, the common ALL antigen (common ALLa) and class II HLA antigens. The remaining 124 cases were also tested with additional markers of T- and B-cell precursors, namely CD7 and CD19. The common leukocyte antigen, T200, was used to exclude nonhemopoietic neoplasms. Cases that remained unclassifiable were further tested with a wider panel of T-cell markers, including CD1, CD2, CD3 and CD5. In some cases multiple mAb directed against the same antigens were used. The relative frequencies of common ALL and B ALL were calculated from the total number of cases and were found to be 39.2% and 3.2%, respectively. The proportions of T-cell and null leukemias were calculated from the better characterized subgroup of 124 cases, and were found to be 50% and 4.8%, respectively. In our series, the age distribution of common ALL revealed a peak at 2-5 yr, but this was partially obscured in the entire series by the high proportion of T-cell cases, which had an age peak between 4 and 12 yr of age. Our results demonstrate marked differences in the phenotypic pattern of ALL in Egypt compared to Western Countries, the predominant finding being a relative excess of T-cell ALL and a paucity of common ALL cases. At present it is not clear whether this results from an increased incidence of T-cell ALL or a decreased incidence of common ALL.