To the Editor: The incidence of acute lymphoblastic leukemia (ALL) varies and the immunophenotypic subtypes differ according to geographical and ethnic settings [1]. The literature regarding people of mixed race is scarce. Brazil has a unique ethnic peculiarity with a large percentage of mixed-race people (black and white), called mulattos. The purpose of the present study was to assess the immunologic profile of this disease among different ages and races in children up to 18 years of age.
Children under 19 years of age with newly diagnosed ALL who were treated consecutively between September 1991 and January 1997 were included in this study. One hundred sixty-six patients with ALL were eligible and 150 of them had the immunologic study completed. They were divided into three groups according to racial aspects: whites (n ס 85), mulattos (n ס 68), and blacks (n ס 13). They were also divided according to age: infants (under 24 months, n ס 21), children (between 2 and 10 years, n ס 110), and adolescents (between 11 and 18 years, n ס 35).
Only samples containing more than 60% of blastic cells were analyzed. Surface immunoglobulin (sIg) was usually identified in direct immunofluorescence, using fluoresceinated goat F (ab)Ј2 anti-human Ig. The presence of intracytoplasmic Ig (cIg) was investigated in direct immunofluorescence on fixed cytospin smears. All other membrane molecules were identified using monoclonal antibodies and indirect immunofluorescence with fluoresceinated goat anti-mouse Ig serum as a second step reagent. The immunologic profile consisted of HLA-DR, CD1, CD2, CD3, CD4, CD7, CD8, CD10, CD14, CD15, CD19, CD20, CD22, CD33, CD34 (Becton Dickinson). Fluorescence activity was analyzed on a FacsCan Becton Dickinson flow cytometer.