The kinetics of blood clearance o isotopically labelled Salmonella entertidis by the reticulo-endothelial system in mice

Abstract

The phagocytosis of ⁵¹Cr or ¹³¹I-labelled suspensions of heat-killed Salmonella enteritidis by the R.E.S. has been studied in mice and the results compared with the kinetic laws which govern the clearance of stable colloid suspensions.

Clearance of bacteria followed an exponential function for the first few minutes, during which about 60 per cent were phagocytosed. Thereafter, the rate of clearance became progressively slower. The maximum extraction by the liver and spleen was calculated as only 48 per cent. Previous administration of heparin slowed the initial clearance of all doses of bacteria exceeding 5 × 10⁷ per 20 g. No inverse relationship between dose and rate of clearance could be shown in either heparinized or normal mice. The greatest proportion of bacteria (70–80 per cent) were taken up by the liver. Bacteria were phagocytosed in preference to carbon particles, but were taken up less readily than heat-denatured albumin (CA). Blood clearance was promoted greatly by previous injection of specific immune serum and slightly by normal guinea-pig serum.

Further investigations suggest that apparent slowing in clearance is due to the fact that not all members of a bacterial population are equally susceptible to phagocytosis.