DISTRIBUTION OF MYOCARDIAL MACROPHAGES IN THE NORMAL HUMAN HEART

Macrophages are important in inflammatory processes in heart disease a nd in transplantation rejection. A resurgence of interest in the macro phage has emanated from recent evidence implicating it as an effector cell in atherosclerosis and transplantation rejection. The detailed di stribution of the macrophage within the normal human heart is unknown. We quantified macrophage numbers in the different chambers of the hea rt. Large tissue blocks (1.5-2.0 cm(3)) were removed from specific sit es in 5 'normal' control hearts (2 males, 3 females, age range 19-46 y ). Paraffin-embedded sections were stained with a CD68 pan macrophage marker. Positive cells were enumerated within 20 random fields. Result s were analysed using a generalised linear modelling method using the Poisson distribution. Macrophages were identified within septa, and of ten close to blood vessels, in the myocardium, and in the majority of areas in all hearts, Macrophage numbers varied significantly between a reas (range 0-6 cells/high power field; P < 0.001), and between the 5 hearts analysed (P < 0.001). In general, there were significantly more macrophages in the ventricles (RV P < 0.01, LV P < 0.05), but these d ifferences were affected by heart differences. This study provides a b aseline for the range of macrophage numbers within normal hearts, thus enabling comparisons with macrophage numbers within diseased and tran splanted hearts.