Reactivity of Anti-Myeloid Monoclonal Antibodies with Committed Hematopoietic Precursor Cells

The development of monoclonal antibodies against surface structures of myeloid cells has contributed to the elucidation of differentiation processes at different levels of hematopoiesis. Most anti-myeloid antibodies have been defined for expression on cells at the stage of terminal myeloid maturation as well as on leukemic cell populations (for review, see Ref. 1). Only in relatively few studies, however, have antigenic structures of hematopoietic precursor cells been investigated with myeloid antibodies (2–8). In addition, the study of hematopoietic precursor cells has been so far mainly restricted to the granulo-monocytic cell lineage. Studies with clonal assays for erythropoietic and megakaryocytic stem cells are lacking in most publications. Furthermore, different in vitro culture techniques may complicate the interpretation of clonal assays even if the antibodies used are directed against the same antigenic structure. For example, a number of antibodies recognize the carbohydrate structure 3-fucosyl-N-acetyllactosamine [1G10 (4), R1B19 (5), VIM-D5 (9)] exposed on committed myeloid progenitor cells. Still the extent of lysis of CFU-GM subpopulations observed in different laboratories with one or the other of these antibodies varies considerably (4,5,8), the main reason probably being differences in the experimental design. For clonal assays of erythroid progenitor cells the situation is even worse since culture techniques using methylcellulose (10), plasma clot (11),or agar (12) are even more difficult to compare.