Distribution of the CD45R antigen in the maturation of lymphoid and myeloid series: the CD45R negative phenotype is a constant finding in T CD4 positive lymphoproliferative disorders.

We have compared the expression of the common leucocyte antigen (CD45) and the restricted leucocyte antigen (CD45R) on normal haematopoietic cells, cell lines, and a total number of 136 cases of myeloid and lymphoid proliferative syndromes. CD45, the conventional leucocyte antigen, presents a generalized distribution along the lymphoid and myeloid maturation pathway with the exception of some myelomas and pre-B leukaemias. In contrast, the expression of the CD45R determinant is more limited. Although it is found in the majority of the differentiation stages of B cells and monocytes, it is present only in the early stages of myeloid differentiation. On T cells it is expressed on mature thymocytes and in the majority of CD8+ lymphocytes and a subset of CD4+ cells on peripheral blood. Finally, our results also indicated that CD4+ T lymphoproliferative syndromes are derived from the CD4+ CD45R- subset (20/20 cases).