EVALUATION OF THE MITOGEN-INDUCED PROLIFERATION AND CELL-SURFACE DIFFERENTIATION ANTIGENS OF LYMPHOCYTES FROM PIGS 1 TO 30 DAYS OF AGE

A study was conducted to characterize aspects of the immune system in the pig from 1 to 30 d of age. Pigs were killed on d 1 (n = 6), d 18 o r 19 (n = 6), and d 27 to 30 (n = 7) of age. Lymphocytes were isolated from the blood, thymus, and spleen. Lymphocyte function was assessed for ability to proliferate as induced by concanavalin A (Con A), phyto hemagglutinin (PHA), and pokeweed mitogen (PWM). Cell surface differen tiation antigens on the lymphocytes were evaluated for percentages of cells expressing CD2+, CD4+, CD8+, and SLA class II molecules. Respons es of lymphocytes from blood, thymus, and spleen to any of the mitogen s were relatively low d 1 through 16; the greatest proliferation occur red by d 28. No detectable percentages of the cell surface differentia tion antigens were found on d 1 and changes varied with age and organ. The results indicate that the porcine immune system is not fully deve loped at birth and the expression of cell surface differentiation anti gens seems to occur before the lymphocytes have the ability to respond to mitogens.