CD45 isoform expression on human haemopoietic cells at different stages of development

Abstract

Alternate splicing and glycosylation produce multiple CD45 isoforms which are selectively expressed on the surface of cells of the haemopoietic system. The expression of CD45RA, CD45RB and CD45RO on CD34+ and CD34- haemopoietic cells from umbilical cord blood, bone marrow and fetal liver were studied by flow cytometry. CD34+ subpopulations defined by CD45 isoform expression were sorted from bone marrow and tested in long-term culture assays. By combining results of functional studies with phenotypic data and previously published information, the following pattern of CD45 isoform expression on early haemopoietic cells was established. The most primitive CD34+ cells are CD45RO+ CD45RB+ and express low or undetectable levels of CD45RA. Upon erythroid differentiation, CD34+ cells remain CD45RO+ CD45RB+, whereas commitment into the myeloid and lymphoid lineages coincides with down-regulation of CD45RO and up-regulation of CD45RA. As a result, the majority of CD34+ cells can be divided into two mutually exclusive populations of cells which express either CD45RO or CD45RA. This notion was confirmed in this study by three-colour immunofluorescence. The alternative expression of various CD45 isoforms on functionally distinct haemopoietic cells suggests an important role for these molecules in the proliferation and differentiation of haemopoietic cells.

Differential long-term and multilineage engraftment potential from subfractions of human CD34+cord blood cells transplanted into NOD/SCID mice

“…Third, T cell potential was apparent in the majority of CD34 ϩ ͞ CD38 Ϫ fractions, but diminished as levels of CD38 expression increased. These findings are consistent with previous in vitro and in vivo studies that have indicated that cells expressing no or low levels of CD38 represent the most primitive fraction of the CD34 ϩ population with respect to colony potential and SRC content, respectively (20,21,(29)(30)(31)(32). These data support recent findings from an elegant set of experiments where retrovirally marked CB was transplanted into NOD͞SCID recipients and identifiable clones exhibited differential periods of longevity (22).…”

“…The CD34 ϩ ͞CD38 Ϫ subpopulation that represents Ϸ5% of the total CD34 ϩ fraction, appears to contain the most immature elements (29,30), including the majority of the long-term cell-initiating cells (LTC-IC) and SRC (20,21,31,32). The CD34 ϩ ͞CD38 ϩ population, on the other hand, is generally considered to represent more mature cells and contains most of the in vitro colony-forming cells (CFC) (31,32).…”

Improvement of Postnatal Neovascularization by Human Adipose Tissue-Derived Stem Cells

“…18 Further characterization showed that the CD34 ϩ /CD31 Ϫ cells lacked the hematopoietic lineage markers CD45 and CD14. 19,20 Moreover, because 20% of the CD34 ϩ /CD31 Ϫ cells also expressed the primitive cell marker ABCG2, it is suggested that the CD34 ϩ /CD31 Ϫ cell population contains a stem cell subset not already committed into a specific lineage. It should be noted that the percentage of CD34 ϩ /CD31 Ϫ cells within the SVF isolated from human AT was markedly higher than in the peripheral blood (at least 500 times higher; personal observations), suggesting that the presence of the CD34 ϩ /CD31 Ϫ cell population is an intrinsic characteristic of the SVF of human AT.…”

Neurotherapeutic Effect of Cord Blood Derived CD45+Hematopoietic Cells in Mice after Traumatic Brain Injury

“…14 The cell membrane protein tyrosine phosphatase, receptor type C (PTPRC) CD45 is abundantly expressed on all nucleated hematopoietic cells and is critical for classical antigen receptor signaling indicated by the arrested development of B and T cells in CD45 deficient mice. 15,16 CD45 isoforms are expressed on human hematopoietic cells at different stages of development 14 and also are involved in regulation of adhesion and motility. 17 Currently, HUCB is a clinically acceptable source of hematopoietic stem cells for transplantations in patients with malignant and genetic or metabolic diseases.…”