GENERAL INTRODUCTION

The haemic system can be visualised as a dynamic three compartment model viz the bone marrow (generative) compartment, the vascular/lymphatic (distributive) compartment and the peripheral organ compartment. This is further sub-divided into cellular subsets comprising erythrocyte, platelet, polymorphonuclear, lymphocyte and monocyte. These cell lineages are defined on morphological, functional and clonogenic characteristics. The relationship of these cell lines to the three compartment model is shown in Figure 1. In addition, the micro-environment of the bone marrow compartment, necessary for normal haemopoiesis, and the haemostatic mechanisms of the peripheral blood compartment are considered parts of the haemic system. Toxic substances exert their effects on the haemic system in many ways. Some may affect only one cell line in one compartment, whilst others may affect all cell lines in all Compartments or alternatively all cell lines in one compartment.

The principle compartments and cellular subsets in which haematotoxicity has been demonstrated by a range of compounds are described below. Since the breadth of scientific and technical information available far exceeds the scope of a single Chapter, experimental methodology has been reviewed in detail for erythrocyte haemolysis and platelet aggregation tests only. The reader is referred to recent reviews cited in the bibliography for details of the many other various in vitro techniques available for the evaluation of the haemic system.