Lymphopoiesis in protein deficiency. Stathmokinetic and tritiated thymidine uptake studies of the mesenteric lymph node of the guinea pig.

In view of the depressed immunity in protein malnutrition, an assessment of the lymphoproliferative activity of the constantly stimulated mesenteric lymph node of the guinea pig was undertaken. A significant reduction of this activity was observed in protein deficiency. a) The germinal centers were reduced in number and size; new formation in the medulla was rarely seen. Lymphoid cells showed lowering of mitotic index and mitotic rate and prolongation of mitotic duration and turnover time. Nuclear labeling with (3)H-thymidine was focal and localized to the peripheral zone. b) Mitotic activity and nuclear labeling were less pronounced in the outer cortex and medulla and least in the paracortical area. Specific uptake of (3)H-thymidine paralleled the low labeling index. c) No appreciable reduction in the number of plasma cells in the medulla was observed. Serum gamma-globulin levels were not significantly altered, but albumin levels were consistently reduced. This was suggestive of preferential preservation of plasma cell activity in the malnourished host. d) There were significant lymphopenia and neutropenia with relative increase of neutrophils in the peripheral blood. This might indicate more severe involvement of lymphopoiesis than myelopoiesis in protein malnutrition.