[Kinetic peculiarities of the immunodepressive effect of methotrexate].

The content of direct plaque-forming cells (PFC) in the spleen of sheep erythrocytes immunized mice after a single administration to them of 2.5 mg/kg methotrexate on the 48th or 72nd hour of the immune response was measured. The PFC count was determined every 4 hours for 68 hours after introduction of methotrexate. In either of the cases the curve reflecting changes of the PFC count in the spleen was of an undulating nature. The alternating rises and falls of the PFC number proceeded at a high speed, viz. the time of doubling and half-periods of drop-off on individual lengths of the obtained curves was of the order of 2--4 hours. It is suggested that the PFC population accretion is ensured by a synchronous recruitment from the cells-precursors, antigen activated upon introduction of methotrexate. The decline in the number of PFC is, apparently, dependent upon their destruction due to an "unbalanced growth".