Development of Antibody-Forming Cells in Neonatal Mice: Stimulation and Inhibition by Calf Thymus Fractions

Crude and purified saline extracts prepared from calf thymus glands, as well as two fractions prepared by disc electrophoresis from the purified fractions, were studied as to their effects on development of antibody-forming cells in neonatal mice. Mice injected at birth with microgram quantities of the purified extract or a stimulatory fraction, prepared by disc electrophoresis, had a 10- to 40-fold enhancement in the number of plaque-forming cells when challenged at 1 or 2 weeks of life, as compared with normal animals. There was also an enhancement of spleen size and weight. Another purified fraction, also prepared by disc electrophoresis and previously found to inhibit lymphocytopoesis, markedly suppressed development of antibody plaque-forming cells in the neonatal mice. The effect was relatively temporary, since older mice injected at birth with this fraction responded normally when challenged with the sheep red cells.