III - Haemopoietic and Lymphatic Systems

Abstract

This chapter deals with the haemopoietic and lymphatic systems. Drug-induced haematological reactions in man include pure red cell aplasia, hypochromic, sideroblastic, megaloblastic and haemolytic anaemias, methaemoglobinaemia, thrombocytopenia and other bleeding disorders as well as leukaemia and lymphoma. Aplastic anaemia is a pancytopenia with completely failed haematopoiesis and an empty bone marrow whereas, agranulocytosis only involves granulocyte production. The importance of the haematological system in preclinical safety evaluation is widely recognized by the routine inclusion of standard haematological tests in toxicity studies. Moreover, like clinical chemistry, haematological study is of practical importance in safety evaluation for it allows sequential monitoring of cellular systems in preclinical and clinical studies with a new drug and forms a useful point of comparison between findings in laboratory animals and man. In addition, human leukocytes are easily accessible for comparative studies of metabolism and drug accumulation. Finally, the effects of drugs and chemicals on the lymphoid and haemopoietic system may be manifested by morphological alterations in the spleen. The central periarteriolar lymphatic sheath (PALS) is a T-cell-dependent area that is well labelled by various anti-T-cell antibodies.