Studies conducted in our laboratory, relating to the development of immune processes in vitamin-deficient experimental animals, have been reviewed.

1) The significant participation of these nutritional factors in the production of circulating antibodies to a variety of antigens, and in the manifestation of delayed hypersensitivity reactions, including the rejection of tissue transplants, has been described.

2) Investigations on the mode of action of vitamin B₆ and pantothenic acid have demonstrated a marked reduction in the production of antibody-forming cells following antigenic stimulation in both deficiency states. The metabolism of antigen appeared to be normal. However, these two vitamins seem to function at different loci in the development of the immune process. Whereas vitamin B₆ appears to be necessary for the production of "C₁" units from serine, which are required for the biosynthesis of nucleic acids, it seems likely that pantothenic acid is involved in the secretion of newly-synthesized proteins into the extracellular compartment.