APPLICATION OF A LOCALIZED HEMOLYSIN REACTION FOR SPECIFIC DETECTION OF INDIVIDUAL ANTIBODY-FORMING CELLS

A technique is described which makes it possible to detect individual antibody-forming cells using a localized hemolysis reaction in a thickened culture medium containing sheep erythrocytes and guinea pig complement. This technique has the advantage over single cell isolation in that it is technically feasible to survey large populations in order to detect a very small active fraction. The cells can be observed continuously during the time of antibody release, and it appears that an estimate of the relative antibody-forming activity can be made from the size of the areas of lysis. Experiments with metabolic inhibitors indicate that active synthesis is occurring rather than release of preformed antibody. Some experiments on the detection of antibody other than anti-red cell antibodies are reported. This technique has been applied to a study of the induction period of the primary response of rabbits to sheep red blood cells. The results of this experiment are consistent with an induction period of 2 to 3 days during which there is no increase in the number of active cells in spleen and lymph node reflecting the lag in appearance of detectable serum antibody followed by an abrupt rise of 50- to 100-fold between the 3rd and 5th day. However, the present data are not sufficient to exclude various other mechanisms.

EFFECTS OF BACTERIAL ENDOTOXINS ON METABOLISM. VII. ENZYME INDUCTION AND CORTISONE PROTECTION

Cortisone acetate administered to mice at the same time as either the LD(50) or 2 x LD(50) of endotoxin significantly protected against lethality. Delaying the injection of cortisone to 1, 2, or 4 hours after that of endotoxin resulted in loss of protection with the possible exception of a 1 hour delay with the LD(50) of endotoxin. Associated with this loss of protection was the failure of the hormone to induce liver tryptophan pyrrolase. Normal mice given only cortisone showed an increase in enzyme activity nearly three times that of control values when assays were carried out either 4 or 17 hours after the hormone was given. Endotoxin-poisoned mice showed normal levels of enzyme activity with concurrent injection of cortisone but depressed levels of enzyme when the cortisone injection was delayed for only 1 hour or more. Apparently, therefore, enzyme induction (or maintenance) is related to survival in endotoxin poisoning. In line with this hypothesis was the observation that inhibitors of enzyme (protein) synthesis were found to potentiate the lethal action of endotoxin and to prevent the protective effect of cortisone. The inhibitors employed were actinomycin D, ethionine, 2-thiouracil, and 8-azaguanine. Activity of liver tryptophan pyrrolase was lowered by endotoxin and elevated by cortisone. When the two were given concurrently, normal enzyme activity was maintained. Chloramphenicol, an active inhibitor of protein synthesis in microorganisms but with limited effect in mammals, was without observable influence in these respects. Mice 18 hours postinfection with Salmonella typhimurium, strain SR-11, given at a level that caused first deaths on the 3rd day, had a lower than normal activity of liver tryptophan pyrrolase and responded to cortisone induction with a smaller increase in enzyme level than that found in control mice. Each is characteristic of endotoxin poisoning. Animals 42 hours postinfection were free of these signs of endointoxication, an observation in agreement with earlier experiments where other measures of endotoxin were employed.