Proposal for basic definitions in experimental hematology.

Abstract

This paper is concerned with basic definitions of cellular stages, processes, and factors in the hemopoietic system from a physiological and operational point of view. In most instances it was also attempted to delineate the relationship between equivalent physiological and operational terms. Such physiological terms were defined for the hemopoietic system, hemopoietic stroma, cell compartment, stem cell, progenitor cell, precursor cell and end cell. The following operational terms were included: hemopoiesis repopulating cell, spleen colony forming unit, transient endogenous colony forming unit, antitheta-sensitive regulatory cell, erythropoietic burst forming unit, granulocyte-macrophage colony forming cell, and marrow fibroblastoid colony forming unit. Subsequently, the following processes were defined: differentiation, maturation, self-renewal, proliferation, regulation and cloning. Moreover, the meanings of macro- and microenvironment of hemopoiesis were explained and definitions of hemopoietic hormones, regulatory cells, such as helpers and suppressors were proposed. Finally, such operational terms were precised as colony stimulating activity, colony stimulating factor, conditioned medium and underlayer. It is hoped that the proposed definitions will be helpful for those readers unacquainted with the specific terminology in the field of experimental hematology and that they will serve as a preliminary step towards international standardization of the terminology in this field.